the general nature and general usage of one form of apparatus in accordance with the invention is illustrated pictorially in fig1 . stated in the most basic terms , optical measurements or readings are taken by use of a manually - manipulatable test instrument 10 which is coupled by cables 12 and 14 to a control unit 16 which includes an input keyboard 18 for actuation and control purposes , a crt visual display 20 on which data may be displayed in various formats , and a housing 22 in the form of a cabinet which encloses associated light sources , electrical supply apparatus , data - handling electronics and data - processing apparatus including for example a microcomputer ( which may be a small digital device of the type known as a &# 34 ; personal computer &# 34 ;, e . g , the ibm &# 34 ; p . c .&# 34 ; or generally similar device ), together with interconnected data storage ( e . g ., floppy disk drive ) and a digital plotter of a conventional nature . with continuing reference to fig1 it will be observed that the test instrument 10 includes a first side or portion 24 , referred to hereinafter as a &# 34 ; component member ,&# 34 ; as well as a second such portion or component member 26 , both of which are disposed in mutually - aligned opposition in this embodiment of the apparatus , and the mutual alignment ( geometry ) selected for the particular application is maintained by support means comprising , in this example , fixed and movable carriers 27 , 27 &# 39 ;, respectively , mounted upon a rigid interconnecting alignment and positioning bar 28 which carries length - measurement indicia 29 . the movable carrier 27 &# 39 ;, to which component member 26 is attached , is slidable along the positioning bar 28 , and a thumb screw or like securement means 30 is provided for fixing this carrier , and thus the component member 26 associated therewith , at a desired point of adjustment along the slide bar , at which the component members 24 and 26 have been positioned in the desired relationship relative to the subject , or patient . in this respect , it is to be understood that the slidable carrier 27 &# 39 ; is maintained in a given desired geometric relationship ( in this example , parallelism ) with carrier 27 , which may be fixed to the end of positioning bar 28 , indexed at the &# 34 ; zero &# 34 ; position of the indicia 29 , such that at any desired position along the length of the bar 28 , the two component members 24 and 26 will be in consistent mutual alignment with one another ( here involving certain axial relationships more particularly described hereinafter ) and that such positioning will be retained upon tightening of the thumb screw or securement means 30 . while many different particular structures or mechanisms might well be utilized for the basic purpose of maintaining a given desired geometric relationship , i . e ., &# 34 ; alignment &# 34 ;, of the two component members while permitting any desired relative movement , one relative basic arrangement for axial relationships is that of a modified dial caliper , having the cross section of bar 28 in the form of a rectangle , and providing a complementary rectangular recess through movable carrier 27 &# 39 ;, such that the complementary shapes permit relative sliding yet maintain the desired alignment . in such an arrangement , a simple threaded thumb screw passing through a threaded aperture in the bottom portion of movable carrier 27 &# 39 ; and aligned to bear against the adjacent edge of the bar 28 will serve as an entirely satisfactory indexing means , permitting the distance between the two carriers 27 , 27 &# 39 ; ( and thus between the two component members 24 , 26 ) to be fixed and easily read visually . the significance of the nominal optical distance information read from the indicia on the bar 28 will be explained more fully hereinafter , but it should be noted that the availability and utilization of this information is decidedly important to the invention . thus , whatever spacial relationship or geometry is desired in a given embodiment , the support , means utilized must be arranged to provide the effective or nominal optical distance , whether the component members are fixed or movable . in the embodiment just described , this information is entered into the computer via the keyboard 18 by the operator , but it may be preferred to utilize a form of the test instrument 10 having a transducer which automatically inputs this information as a coordinated part of the overall procedure . as may further be seen in fig1 the test instrument 10 is utilized to place the two component members 24 and 26 on opposite sides of the breast or other such body extremity which is to be examined pursuant to the present invention . in the case of the human female breast , several different readings are preferably taken , for purposes discussed more fully hereinafter , at four positions : centrally of the breast and near the chest wall ; on the inside edge or marginal extremity of the breast ( i . e ., on the side nearer the center of the chest ); along the outer marginal edge of the breast and generally across from the inside measurement just noted ( both such measurements preferably being accomplished at a relative position somewhat further out from the chest wall than the first reading noted ); and at a location which is generally centrally of the breast but as far outward from the chest wall as practicable , behind the nipple . in this respect , depending upon the particular anatomy of a given patient , certain such readings may at least slightly overlap , although in other cases they will not . the orientation of the test instrument , and of the two component members , is preferably generally vertical in these different measurements or readings due to the interstructure of the breast , which is much more symmetrical from one vertical section to the next . thus , the instrument is moved from place to place by manual manipulation , in each instance the two component members being moved apart to the extent necessary , placed over the breast in the desired positioning , and then gently moved toward one another to the extend necessary to provide full contact between the inner surface of each component member and the breast , so as to preclude the entry or exit of any light from between the breast and each of the component members . the component member 24 is seen in more detail in fig6 , 8 and 9 . as seen there , the structure of this member includes a cylindrical outer shell or cover 32 which is closed at one end ( the rear , as referred to herein ) by a circular connector deck 34 , and which at its other end has a forwardly projecting cylindrical nosecone 36 whose central opening may be covered by an optical filter 38 , an element primarily useful for environments having ambient lighting which would interfere with the optical responses to be obtained . for example , under such conditions a &# 34 ; safe light &# 34 ; may be used in combination with a complementary filter ; e . g ., a blue - green safe light where infrared light is most important , complemented by an orange filter as element 38 . the outer shell or cover 32 may be a thin metal member , and the connector deck 34 may also be of metal , preferably brass or aluminum , to provide for optimum electrical grounding . the nosecone should be of a material which is opaque to infrared light energy , such as for example a filled epoxy , and the nosecone and outer shell should telescope snugly together and may be slightly tapered to enhance a close - fitting relationship . inside the outer shell 32 and the nosecone 36 is a generally flat support plate 40 which bottoms against the connector deck 34 on one end and directly contacts a circular detector deck 42 , to which it is secured in a desired manner , as by adhesive or screws , and the peripheral edge of the detector deck seats in and against the edges of an annular shoulder formed in the inside of the nosecone . the support plate 40 is likewise secured at its opposite end to the connector deck 34 , which has a peripheral shoulder which snugly receives and seats the end of the outer cover 32 , such that the entire assembly is a rigid unit , around which an annular upper portion of the carrier 27 fits , and is secured . inside the component member 24 is the forward end extremity of an optical fiber cable or bundle 44 , which enters through an appropriate aperture in the connector deck 34 and which projects forwardly , generally parallel to the support plate 40 ( to which it may be secured by an appropriate clamp [ not shown ]), beyond which it passes through both the detector deck 42 and the filter plate 38 , preferably terminating om a stainless steel or like ferrule 46 . also , within the component member 24 , is a pair of optical detectors 48 and 50 , which seat within appropriate apertures in the detector deck as well as in appropriate grooved or recessed portions in the end of the support plate 40 . the detectors have electrical leads or conductors 52 which exit the component member through the connector deck 34 , preferably through an appropriate connector 53 . at the forward end of the component member , a thin plate - like septum 54 is fixed into position between the forward surface of the detector deck 42 and the rearward surface of the filter 38 to provide optical isolation of the detectors 48 , 50 from the optical fiber bundle 40 , and this effect is furthered by providing an arcuate reception slot 56 extending through the filter plate 38 , through which light energy must pass in order to be received by either of the detectors 48 and 50 . arcuate slot 56 is in fact a segment of a circle which is centered upon the optical fiber 44 and the distance ( radius ) between the optical fiber cable and the reception slot should , in the embodiment under discussion , be in the range of about one to three centimeters , preferably not more than about two centimeters . this distance is important , since in this embodiment the detectors 48 and 50 are &# 34 ; near &# 34 ; detectors whichare intended to receive directly - returned ♭ reflected &# 34 ; light energy , i . e ., light which has been introduced (&# 34 ; injected &# 34 ;) by the optical fiber bundle 44 into the particular body portion or extremity with respect to which clinical data is desired to be obtained , and which has in fact entered that body portion and has encountered initial reflection and &# 34 ; backscatter &# 34 ; from the internal tissue directly beneath the skin . thus , the &# 34 ; reflected &# 34 ; light energy detected by &# 34 ; near &# 34 ; detectors 48 and 50 has passed through the skin of the subject to enter the internal tissue of the breast ( or other body portion ) but has immediately exited by passing back outward through the skin toward the source . this &# 34 ; near &# 34 ; detection signal is very important in accordance with the invention , as will be explained more fully hereinafter , and should not include light which has merely passed directly from the end of the fiber optic , over the end extremity of the septum 54 , and directly into the detectors 48 and 50 without ever having passed into and out of the skin of the subject . also , in this embodiment , the detected light energy should represent light reflected immediately back at the source , which has not traversed substantial distances within the breast tissue itself and emerged far away from the source ; consequently , the reception slot 56 and the detectors 48 and 50 themselves should not be located more than the indicated distance from the point of light injection . the &# 34 ; direct transmission &# 34 ; ( i . e . the &# 34 ; far &# 34 ;) detector component 26 for the embodiment under discussion is illustrated in fig2 , 4 and 5 . this member is substantially the same in basic structure as component 24 discussed above , including an outer shell 32 &# 39 ;, a circular connector deck 34 &# 39 ; at the rear through which an electrical cable 14 enters and exits the component member , preferably via an appropriate connector 53 &# 39 ;. within component 26 is a support plate 40 &# 39 ; and a detector deck 42 &# 39 ;, all secured together generally in the manner discussed above with respect to component 24 . in the case of this &# 34 ; far &# 34 ; component member , however , four detectors are preferably present , i . e ., detectors 58 , 60 , 62 and 64 , all mounted generally in the manner referred to above with respect to detectors 48 and 50 , i . e ., protruding through the detector deck 42 &# 39 ; and disposed within appropriate recesses in the forward end of the support plate 40 &# 39 ;. as in the case of component member 24 , component member 26 also includes a septum , designated 54 &# 39 ;, but in this case the septum separates and helps to optically isolate pairs of detectors , as best illustrated in fig5 detectors 58 and 64 being in one such pair and detectors 60 and 62 being in the other such pair . in the case of component member 26 , a filter plate such as that previously described ( and designated by the numeral 38 ) may also be used if necessary , depending upon circumstances involved in the test environment , but is not included in fig2 and 5 . it should be understood that terms used herein such as &# 34 ; direct &# 34 ; or &# 34 ; transmitted &# 34 ; and &# 34 ; reflected &# 34 ; or &# 34 ; scatter &# 34 ; are adopted primarily for purposes of convenience and illustration , and not to indicate that there are fundamental differences between the light energy that emerges at any given point from the selected body portion after injection . actually , it is believed that all injected light undergoes multiple and diverse scatter effects throughout its tortuous path of propagation within the breast or other body portion in which it has been injected . thus , the present invention contemplates use of the overall optical response provided by comparitive analysis of the &# 34 ; near &# 34 ; and &# 34 ; far &# 34 ; detection signals , which response is viewed as complex in nature and quite conceivably involving molecular ( rayleigh ) scattering , particle ( mie ) scattering , index ( fresnel and christiansen effect ) scattering , fluorescence ( especially infrared fluorescense ), inelastic ( raman ) scattering , and both spectral and non - spectral energy absorption . thus , the circumstances and the methodology are considerably more complex than simple in vitro laboratory spectrophotometry , and the responses profiled in accordance herewith may well depend upon such factors as molecular structure , the types and size distributors of cells , the amount , nature and distribution of fat cells and of connective tissue , the blood supply and vascularization metabolism , the lymph system , and glandular activity . the optical fiber cable 44 referred to above in conjunction with fig6 , 8 and 9 is seen in somewhat more detail in fig1 , which illustrates that the aforementioned ferrule 46 terminates a brief distance inward from the actual end of the bundle of optical fibers 144 , corresponding to the thickness of the filter plate 38 . the main bundle 144 of optical fibers is preferably sheathed , as for example by a flexible helical conduit 66 extending over that portion outwardly of the cabinet 22 ( fig1 ) and an external sleeve 68 of plastic or the like may be utilized for stress relief . a mounting flange 70 is shown to illustrate a preferred structural attachment of the optical cable to the cabinet 22 , and the portion of the cable which is to be disposed within the cabinet may simply be covered by protective cladding or lightweight tubing 72 . as illustrated ( fig1 ) this latter portion may be divided into more than one branch ( three being illustrated ) in the event multiple light sources are to be uitilized , each branch terminating in appropriate light - coupling optical terminals 73 , 74 and 75 , which may be physically sized differently from one another in a manner best suited to optically match the particular source to be coupled thereto . as indicated previously in conjunction with the discussion of fig1 the component members 24 and 26 are in the particular embodiment under discussion , held in direct alignment with one another by the carriers 27 , 27 &# 39 ; and the bar 28 . more particularly , in this embodiment the alignment is such that the light - injecting fiber optic 44 is substantially aligned along the same axis with one pair of the &# 34 ; far &# 34 ; detectors , e . g ., detectors 58 and 60 , the other such pair of detectors thus being disposed a predetermined distance off - axis . this is for purposes of comparison and data - enhancement , as pointed out more fully below . in accordance with a particular aspect of the invention , one or more different light sources may be utilized to provide a relatively large number ( on the order of about twenty ) of different wavelength spectra ( spectral groupings ) within the total spectrum of about 0 . 5 microns to perhaps 2 . 2 microns , and particularly within the range of about 0 . 6 to 1 . 5 microns , the wavelength resolution preferably being on the order of about 15 nanometers ( nm ) in the visible range and about 30 nm in the infrared range , which spectral array is conducted through the optical fiber cable 44 to the component member 24 , from which the different light spectra are sequentially injected into the body portion under examination , e . g ., a breast . that is , each such source scans or steps through its particular different wavelength groupings one after another , with a relatively brief &# 34 ; dwell &# 34 ; for each particular different grouping . accordingly , the various detectors will produce outputs in a corresponding sequence , each particular such output thus being correlated to and representing a measure of the intensity of the light energy received at a particular detector location as a result of a particular narrow wavelength grouping of light injected or admitted . with respect to particular examples of light sources , use of scanning monochromators and an interference filter wheel are contemplated , for example in an arrangement where each provides a portion of the overall desired wavelength spectrum . an ocli variable filter wheel may be the most preferably monochromator , at least for the &# 34 ; visible &# 34 ; light portion of the spectrum desired ( and possibly for certain of the &# 34 ; near &# 34 ; infrared spectra ) because of optical efficiencies provided which will increase the amount of light injected . the light sources themselves should be &# 34 ; chopped &# 34 ;, as by an optical shutter ( rotating apertured disc ), to reduce low - frequency background and &# 34 ; common mode &# 34 ; noise , and the detectors should thus be switched synchronously with the chopping of the sources . somewhat more particularly , with respect to the particular source of illumination , a tungsten filament quartz - halogen lamp may be utilized , with imaging of the filament onto the entrance apertures of the monochromators , with optical power input to the body portion under examination running from aout 1 . 4 milliwatt at the lower end of the spectrum to about 1 . 9 milliwatt through the visible portion of the spectrum and perhaps on the order of about 3 to 31 / 2 milliwatts over the infrared portion of the spectrum ( depending upon the thickness of the body portion being scanned ). the optical filter selected for use should desirably augment the source over the infrared portion of the spectrum , with particular filters being cut to the various water windows and water absorption bands involved . that is , as illustrated in fig1 , it is known that contrary to what a lay person might expect , ordinary water has the property of varying transmissibility to light , having several very pronouned &# 34 ; absorption bands ,&# 34 ; i . e ., strong light - absorption characteristics , at particular wavelength bands , separated by &# 34 ; windows &# 34 ; in which the transmissibility increases markedly between the preceding absorption band and the next succeeding one . referring more particularly to fig1 , considering the transmissibility of water for varying distances at wavelengths from 0 . 8 microns to about 2 . 5 microns , at distances ranging from 1 millimeter ( top curve ), 3 millimeters ( second from top curve ), 10 millimeters ( second curve from bottom ) and 30 millimeters ( lowermost curve ), strong absorption bands will be seen to exist over areas designated a1 , a2 and a3 , occurring at approximately 0 . 9 - 1 . 0 microns , 1 . 4 - 1 . 5 microns , and 1 . 9 - 2 . 1 microns . between these absorption bands , strong transmissibility &# 34 ; windows &# 34 ; may be seen at approximately 1 . 0 - 1 . 3 microns , 1 . 7 - 1 . 8 microns , and at about 2 . 2 microns . the absorption bands and transmissibility windows will thus be seen to produce striking results , since at transmission distances of 1 millimeter and 3 millimeters , light is substantially fully absorbed at wavelengths of approximately 1 . 5 microns and approximately 2 . 0 microns , but a very strong ( by comparison ) transmissibility band exists between these wavelengths . these characteristics have more than casual significance to methodology such as is contemplated herein , since human body is of course comprised of a preponderance of water , and transmissibility characteristics of human tissue must therefore be anticipated as exhibiting somewhat similar characteristics , or in any event as encompassing the same technological phenomenon . in this respect however , it should be noted that different types of tissue embody different water content ; for example fatty tissue has much less water and it is less tightly bound by the molecules ; thus , fat tissue exhibits much greater optical transmissibility per unit thickness than does glandular tissue , for example . that is , the type of water binding involved in the tissue of a particular body portion will significantly affect the optical response , particularly transmissibility , since tightly - bound water has a much different response than weakly - bound or free water . an example of water content affect on a more general basis may be seen in fig1 , in which the transmissibility of fused quartz of one meter length is illustrated for two different gradations or degrees of quartz purity , namely , two parts per thousand water ( left - most curve ) and three parts per million water ( right curve ). in view of this , it should be understood that the fiber optic bundle used in accordance herewith should be of the latter type , i . e ., having very minimal water content . fig1 is further illustrative of conditions to be encountered , showing the general characteristics of , and marked differences between , the response of oxygenated hemoglobin on the one hand and reduced ( oxygen depleted ) hemoglobin on the other hand within the range of 600 nm to 850 nm , actual crossover of the response curves being present . as may well be perceived by contemplation of fig1 , 12 and 13 , attempted optical ( light transmission ) examination procedures in living tissue will inevitably be highly affected , even to the extent of obscuring meaningful results , if accountability of water absorption and oxyhemoglobin characteristics is not fully considered . in particular , the water absorption windows must be taken into account , preferably by eliminating the effects from the test instrumentality itself ( i . e ., choosing optical fibers having the least adverse response ), and by the aforementioned approach of selecting the optical filters on the basis of the water absorption bands and transmissibility windows . a further and analogous consideration is the noted absorption characteristics of oxygenated and reduced hemoglobin , which is of course present in great abundance in living human tissue and which should thus be similarly taken into account , either by avoidance or by appropriate compensation in the analysis of the resulting data . to a substantial degree , a primary aim of the present invention is to obtain clinical , physiological data for selected body portions , and particularly of the female breast , by optical response methodology , and in a more particular sense , to obtain such clinical data on the basis of intrinsic , internal tissue properties ; that is to say , to produce data which will be applicable from one individual to another , for widely - based comparison and classification . this requires that the data be free of the effects of individual particularities such as for example , skin differences , including pigmentation , color , thickness , etc ., as well as breast thickness , and other particular physical characteristics . such an achievement is of fundamental importance in pursuit of the particular type of methodology involved here ( i . e ., optical response analysis or study of living subjects , and in particular of living human subjects ), since without these essential refinements , there can be no truly meaningful correlation between any two different individuals having a normal range of individual differences . in accomplishing the aforementioned objective , the above - disclosed method and apparatus for readily determining ( reading out , or establishing in advance ) the particular distance between the component members of the optical probe ( i . e ., the &# 34 ; nominal optical distance &# 34 ;) involved in a given measurement or scan is of surpassing importance , as is the determination and appropriate usage of both &# 34 ; direct &# 34 ; light transmission or propagation data ( i . e ., &# 34 ; far &# 34 ; data ) as well as &# 34 ; reflective &# 34 ; ( i . e ., &# 34 ; near &# 34 ;) data . with respect to the second such point , a significant feature of the present invention is the realization that &# 34 ; reflected &# 34 ; ( i . e . &# 34 ; near &# 34 ;) transmissibility data should be obtained and in effect used as a measure of the light energy actually injected into the interior of the body portion under examination , after the effects of impingement upon and passage through the skin , etc . from this &# 34 ; near &# 34 ; detection level is substracted the &# 34 ; far &# 34 ; or &# 34 ; direct - transmission &# 34 ; data , since by so doing one may compare the amount of light energy which has passed completely through , or at least traversed a substantial portion of , the breast or other body portion to the amount of light energy actually injected into the internal tissue initially , and thus remove from consideration all of the many data - modifying characteristics arising from individual differences of skin . this in effect provides data which is truly a gauge of intrinsic , internal tissue characteristics , which may be accurately correlated with similar data taken from other different body locations and / or other individuals . furthermore , the knowledge and appropriate utilization of the particular nominal optical distance involved in each different optical scan over whatever different wavelength spectra have been selected and over whatever different body portion or path has been selected is similarly of great significance , since this optical distance is utilized in accordance with the invention to in effect further normalize or condition the data obtained and thus remove the otherwise inherent variation of light energy propagation as a function of optical distance or thickness . in this connection , it should be clearly understood that the particular arrangement illustrated , with axial alignment of the receivers and close positioning of the &# 34 ; near &# 34 ; detector to the light source , is not at all the only effective such arrangement . that is , while at least one &# 34 ; near &# 34 ; and one &# 34 ; far &# 34 ; detector are required , they need not be positioned on a straight - line basis if some other ( e . g . relative angular positioning with respect to the light source ) arrangement is desired , as for example to better accommodate a particular anatomical area to be studied . in any such arrangement , the effective or nominal optical paths involved for the particular positions of the receivers must be determined , and the difference between such optical distances determined , since that difference ( representing the different tissue volume sampled by the far receiver ) is the essence of what is intended by use of the term &# 34 ; optical distance &# 34 ; herein . that is , in the particular example illustrated the close proximity of the near detector to the point of light injection may either be assumed to represent a zero optical distance for that detector or else the very short actual distance for it may be &# 34 ; built into &# 34 ; the scale which is read to determine the optical distance for the &# 34 ; far &# 34 ; detector . in any case , utilization of the measured or otherwise - determined effective or resultant optical distance is accomplished both by using it to compensate for inverse square reduction of propagated light intensity and also as the &# 34 ; thickness &# 34 ; parameter in application of the exponential function attributed to beers and known as beers &# 39 ; law , to develop intrinsic light propagation magnitude values for the internal tissue of the selected body portion . while it is not the purpose of this disclosure to focus upon any particular methodology and / or apparatus for actually making this data compensation or specifically implementing the data - conditioning principles , it may be noted that data - handling procedures of this general nature are readily and indeed routinely obtained through use of known techniques and routines in the use of digital computers , and that appropriate results may also be obtained directly through electrical signal - processing approaches , in hardware ( circuitry ), since discrete digital components such as adders , subtracters and digital dividers are of course in widespread use and widely diverse availability . it is the general underlying principle and methodology of such approaches which is here involved , i . e ., arrival at intrinsic - type data by conditioning the signal values actually received from the &# 34 ; far &# 34 ; receivers in the &# 34 ; direct transmission &# 34 ; mode through use of the &# 34 ; near &# 34 ; receiver &# 34 ; reflectance transmission &# 34 ; data , together with use of the nominal optical distance measurement determined for each particular measurement set . further aspects of the methodology involved in the present case are the aforementioned concepts of taking multiple different data scans at different predetermined positions on the same body portion ( in particular , the human breast ), as well as on comparable or complementary body portions on the same person ( e . g . the opposite breast ) and by use of similar scans taken at like positions on like portions of other persons ( and including averaged or composite such scans , classified as by age or condition for example ), all obtained by use of the same or substantially the same spectral transmissibility procedures , involving numerous different wavelengths of light with resulting multiple data points on a wavelength - specific basis , with subsequent presentation of the resulting data in the form of graphical or tabular profiles for study and consideration in documenting the characteristics of a given person at a given point in that person &# 39 ; s life , together with analysis for determination of individual characteristics and anomalies present at the time of the particular scan or set of readings . in this respect , the resulting data , to be commented upon more specifically herebelow , may advantageously be displayed both by tables of magnitudes and by plotting the compensated and weighted magnitudes with respect to wavelength , not only by means of separate graphical presentations for each different location from which data is obtained , but also by taking complementary scans of complementary body portions , i . e ., in the case of breast examinations , by taking a set of measurements for both breasts with similar relative positioning of the hand instrument 10 , i . e ., both left and right breasts along the inner ( central ) marginal edges , along the outer marginal edges , centrally near the chest wall , and centrally outward away from the chest wall . the resulting data provided in accordance with the invention may also be presented in the form of color maps , by use of known color - mapping programs commercially available for digital computers of the type referred to herein . for example , the data obtained for particular wavelength groupings may be assigned different colors , and the colors overprinted within a map area as a function of received signal intensity after conditioning as described hereinabove . this will yield yet another form of data presentation which will have widely - differing color content and distribution , according to the characteristics of the tissue sampled , which will have different evaluative effects for different persons which may be preferred by some . regardless of which particular form of data presentation is selected , the formatted data may then be meaningfully compared to similarly formatted data for the same patient , and the records so obtained preserved for comparison with similar records taken at other points in time . further , such results may be comparitively examined with respect to other results obtained from other particular individuals , both those who may be known to be &# 34 ; normal &# 34 ; ( i . e ., not known at that time to possess specific and identified abnormality or disease ), as well as for those who may have diagnosed abnormality or illness . a further point in the foregoing connection involving the particular methodology and apparatus disclosed herein , relates to the use of duplicative or dual reception means at the different locations in the component members 24 and 26 , as already mentioned generally hereinabove . that is , considering the total spectrum of the various wavelengths which may be utilized in accordance with the invention , as noted above , it has been determined that each of the &# 34 ; sets &# 34 ; or &# 34 ; pairs &# 34 ; of detectors at both the far transmission receiver , or component member , 26 and also at the near receiver or component member 24 are preferably comprised of two different types of detector elements , one of which is more effective over the shorter wavelength portion of the spectrum and the other of which is more effective over the longer wavelength portion , with an area of commonality or overlap in the midrange . for example , silicon photovoltaic cells are desirable for receiving the chopped &# 34 ; visible &# 34 ; light wavelengths of from about 0 . 5 to about 1 . 2 microns , while lead sulfide ( pbs ) photoconductive cells provide some advantages in the higher , infrared wave length ranges , actually providing useful results throughout the range of from about 0 . 85 to about 2 . 2 microns , even though involving substantially higher noise production than the silicon photovoltaic cells . a possible alternative to the lead sulfide cells ( detectors ), may be a zero - bias germanium photovoltaic cell , whose band gap is essentially midway between silicon and lead sulfide , and which may be cooled to lower the effective noise equivalent power . such germanium detectors would not provide detection to the longer wavelengths over which lead sulfide is operative , but does have the advantage of having a peak response in the neighborhood of about 1 . 5 microns , which may be at or near the only water transmissibility &# 34 ; window &# 34 ; beyond the 1 . 3 micron point . an alternative for the silicon photovoltaic cells is the silicon photodiode , having somewhat similar performance as the silicon photovoltaic cells , although they are presently deemed more preferred . the dual - detector configuration just noted not only serves to produce useful data over a greater wavelength spectrum , but also has the added feature of providing redundant data over a shared midrange . to be sure , the absolute magnitudes of signals produced by the dissimilar types of detectors will be significantly different , but this of course may readily be balanced or compensated for by appropriate level - setting or gain - control procedures ; consequently , the duplicative or redundant data produced over a certain portion of the transmitted wavelength spectrum , received at essentially the same position with respect to the light emitter or injector , is considered to be highly useful , since the data may be mutually compared to detect error sources , etc ., and it may also be averaged together in order to increase accuracy and reliability . this same goal is served by providing the four - detector set in the &# 34 ; far &# 34 ; or &# 34 ; direct transmission &# 34 ; receiver or component member 26 ; that is , the &# 34 ; on - axis &# 34 ; set of detectors ( comprising two different types of detectors , as discussed above ) samples data from a conceptually different point ( i . e ., coaxially with the fiber optic ) than does the adjacent set of &# 34 ; off axis &# 34 ; detectors ( which also comprise two different types of detectors ). the data obtained from these two conceptually differing detection locations may also be compared and averaged or combined in the general manner discussed above with respect to the two different types of detectors , at each different detected wavelength , i . e ., each different narrow wavelength band comprising a step or unit of the light injected into the body portion under examination by the fiberoptic cable . other techniques which take further advantage of the dual - dissimilar detector configuration are for example , a sequence of blocking first one and then the other with optical filters at selected points in the wavelength transmission spectrum , to provide greater flexibility and certainty for data - comparison and evaluation techniques . where more than one specific light source is utilized , as for example two different monochromators , such blocking and filtering techniques may be utilized to insure transmission channel separation . it should be further noted that the silicon photovoltaic cells preferred for detection at the lower portion of the spectrum require a lower &# 34 ; chopping &# 34 ; frequency of the light source than do the lead sulfide photoconductive cells , due to the higher capacity of the silicon cells . for example , a useful frequency for use with the silicon cells is on the order of 13 hz , whereas an optimum chopping frequency for the lead sulfide cells is on the order of about 220 hz . as will be understood , the output provided by each individual detector will comprise a series of magnitude or intensity readings measuring the amount of light energy received at that detector at the various points in time corresponding to the wavelength spectra produced by the light sources and injected into the body portion under examination . this analog - form electrical signal is conducted by the particular electrical lead or conductor within the electrical cable 14 which is associated with the particular detector involved . in this connection , it is to be noted that the component members 24 and 26 are , in the form illustrated , particularly sized to accommodate preamplifier circuitry , and additional processing circuitry if desired , within the enclosure or space 65 behind the detector element itself and alongside the support plate 40 in each component member . the resulting electrical signal , which is at least initially of analog form , is coupled by the electrical cable 14 back to the control cabinet 22 noted previously , which includes signal - processing and computing electronics , as well as the display apparatus already noted hereinabove . alternatively , it should be noted , the light detection may be accomplished through use of fiber optic receivers , with the received light energy conducted back through such fiber optic to the detection circuitry , where the detectors would then be located . preferred signal - processing circuitry for the detector signals should include dedicated channels for each detector output , preferably of a type treating the detectors as current sources and including as entry - level components low - noise operational amplifiers such as the ad515h , to whose inverting input the detector output should be applied . this amplifier configuration will appear as a very low - impedance load to the detectors ( essentially , a short circuit ), and thus , with the operational amplifier connected in a current - feedback mode , virtually all of the signal strength will be shunted through the feedback resistor , such that the current output for the detectors will be linearly related to the input optical power . after such amplification , the detector outputs ( which will , of course , reflect the chopping applied to the illumination sources ) is preferably compressed by applying it to a logarithmic - function analog ic , following which it is converted to digital form by use of an a / d converter operated in a sampling mode at twice the chopping frequency and synchronized with the light source choppers . the logarithmic conversion before digitization , although not strictly essential , serves to expand the dynamic range of the data obtained from the detectors . reconversion to linear form may be accomplished by use of a digital anti - log ic , and the resulting data stream should be put through a subtraction stage in order to remove common mode ( background ) signal , after which the data should be averaged over a number of chopping cycles equal to one percent of the wavelength scan time . thus , the final data for any given detector will consist of strings of repetitive bursts , each representing averaged detection signals from which background signal has been subtracted . a desirable addition , or alteration , of the signal - processing electronics described above is to demodulate the chopped signal and integrate the result over a number of the chopping cycles before the initial logarithmic conversion . in the case of the lead sulfide detectors , it may be advisable to omit the logarithmic compression step , and go directly to the a / d conversion , due to the presence of substantial noise and the limited extent to which the total dynamic range they provide may be utilized , due to water absorption characteristics in living human tissue , particularly in actual in vivo examination of human anatomical portions . this is particularly true with respect to the female breast , which undergoes almost constant physiologic change both on a day - to - day monthly basis and , to a much greater extent , over a lifetime , there being great differences in the relative amount of water present from time to time , as well as in its form , which may be free or &# 34 ; bound ,&# 34 ; e . g ., in protein molecules . an example of typical ( if somewhat simplified ) data to be obtained from actual clinical measurements done in accordance with the present invention is depicted in table i immediately below , which should be understood as showing relative magnitudes of detector data obtained at four different examining positions , as identified , on both the right and the left breast of a human subject . in this instance , the data in rows 2 and 6 was obtained near the chest wall at essentially the midportion of the breast , and the data in rows 4 and 8 was obtained at generally symmetrical upper and outer quadrant portions , rather than at the central and outer position identified above as now preferred for a fourth data - taking position . also , instead of obtaining individual data readings at many different wavelengths , the numerical data presented may be taken as indicative of the maximum reading obtained by use of a single wavelength grouping or band under the indicated conditions , such maximal data ( which is also representative of composite or weighted averaged data ) having very evident significance even though being generalized or simplified when compared to the numerous individual readings at different wavelengths which the complete data scan described above would include . in either event , expressions such as &# 34 ; selected light wavelengths &# 34 ; are used generally in accordance herewith to designate any such procedure , regardless of how many wavelengths may actually be selected in a given application , and not merely to identify a procedure using all or a major portion of the particular wavelengths identified as making up the total useful spectrum for the methodology involved . table i______________________________________exemplary data fromclinical measurements &# 34 ; direct &# 34 ; &# 34 ; reflec - ( i . e . far ) tion &# 34 ; direct / aver - trans - ( i . e . reflec - age mission near ) tion ( per - data data ( percent ) cent ) ______________________________________right1 outer portion 386 3850 10 . 03 ( outer third ) 2 mid - portion 147 4564 3 . 22 8 . 89 ( middle ) 3 inner portion 514 3834 13 . 41 ( inner third ) 4 other 299 2015 14 . 84left5 outer portion 1206 2571 46 . 91 ( outer third ) 6 mid - portion 680 1976 34 . 41 43 . 04 ( middle ) 7 inner portion 1431 2993 47 . 81 ( inner third ) 8 other 975 3157 30 . 88______________________________________ consideration of the data in the above table will readily reveal the significance of the readings as a general indicator of condition . thus , in comparing the readings in rows 1 and 5 , for example , for the outer third of the right breast in comparison to the left breast , the differences in numerical magnitude shown reveal graphic differences in the underlying physiological conditions . further significance can be drawn by comparing in a relative manner the &# 34 ; direct &# 34 ; ( or &# 34 ; far &# 34 ;) transmission data and the &# 34 ; reflection &# 34 ; ( or &# 34 ; near &# 34 ;) transmission data at each given sampling station , and for the same station on opposite breasts . the actual numerical ratio of &# 34 ; direct &# 34 ; transmission data to &# 34 ; reflection &# 34 ; transmission data is indicated in the third column of figures , and differences here are readily apparent upon casual examination ; the same is certainly true with respect to the figures in the fourth column , which are the overall percentile averages of data for rows 1 , 2 and 3 and 5 , 6 and 7 , respectively . in fact , this data is actually representative of measurements ( data ) obtained under clinical conditions from a living person ultimately diagnosed by other and conventional methodology to have carcinoma of the right breast . fig1 illustrates another useful approach in presenting data obtained in accordance with the invention , providing a series of graphical &# 34 ; profiles &# 34 ; for each patient or individual on the basis of paired curves for each different position of the examination instrument , the two curves in each pair representing the data for the two breasts of the same patient obtained at the same position of examination . these pairs of curves may be displayed on the crt screen 20 immediately after the corresponding scan has taken place , and / or they may be plotted out on paper in the general form here shown , for a permanent record . of course , the data itself may also be stored in digital form on a suitable record , e . g ., magnetic disc or tape . fig1 includes three individual sub - figures , designated 14a , 14b and 14c , each showing data readings obtained from a different subject ( person ) under clinical conditions , the three sets of data being generally illustrative of different physiological conditions likely to be encountered in the general population . in these sub - figures , each vertical column represents data obtained from a different person , and each horizontal row shows data obtained at the same general location each of the three different individuals . in each individual graphical presentation there are separate traces or &# 34 ; curves &# 34 ; for each breast , the right breast data being shown in a darker , heavier line , and the left breast data being shown by a lighter , finer line , as indicated in the legend in the upper left - hand corner of the page ( i . e ., &# 34 ; rt &# 34 ; and &# 34 ; lt &# 34 ;). each individual curve or trace represents composite detector output signals obtained at a different examination wavelength or , more particularly , at a particular step in the examination scan comprising one increment of the entire examination wavelength spectrum . in these graphical presentations , the ordinate represents detector output and wavelength is represented by the abscissa , although it is to be understood that such &# 34 ; detector output &# 34 ; comprises the intrinsic valuations referred to previously , involving compensation or conditioning based on nominal optical distance and the &# 34 ; near &# 34 ;-&# 34 ; far &# 34 ; data resolution described above . also , the scale values for the ordinate and abscissa are not the same in the three different columns , the different curves having in effect been centered or partially centered in the available space for simplicity and uniformity in these drawings . thus , in actual practice , different curves plotted on the same continuous and dimensionally consistent axes would show even greater differences for different patients since the location of some curves will be considerably different than others with respect to the particular position in the field defined by the ordinate and abscissa , depending upon the particular physiological conditions encountered in a given patient . considering the graphical representations of fig1 in somewhat more detail , it will be noted that the two different tracings for the right and left breast , respectively , appear very symmetrical in the left column ( fig1 a ); indeed , the two traces are very nearly in registration with one another in almost all areas , apart from some magnitude differences in the top reading , obtained at the &# 34 ; inner &# 34 ; position ( i . e ., center of the breast and near the chest wall ). even so , the relative shape of the traces very much resemble one another , with the exception of some very slight divergence for the &# 34 ; outer &# 34 ; position ( center of the breast and away from the chest wall ) at the longer wavelengths . some of the same general observations may be made with respect to the clinical data presented in the center column ( fig1 b ), although it will be noted that the two traces do not come into such close registration , and there are more differences in the shape of one curve compared to the other . these general characterizations are muchless true with respect to the data presented in the right - hand column ( fig1 c ), in which some readily apparent and significant divergence in curve shape is present , portions of the two different curves actually having oppositely - directed slopes of considerable steepness . even from considering the curves in this rather superficial manner , and making even such generalized observations , it may not be surprising to learn that the actual patients involved were , in the case represented by columns 14a and 14b , relatively &# 34 ; normal &# 34 ; women of different ages and different breast composition ( e . g ., different amounts of glandular and / or fibrous connective tissue as compared to fat ); in the case represented by column 14c , however , the data represents an older woman diagnosed medically as having certain breast abnormality or anomaly in each breast , of which that on the right side appeared more serious . it is believed self - evident that consideration of the results indicated above demonstrates not only the presence of meaningful data but also the potential of a highly useful methodology . in this respect it is not the purpose of this specification to assert a complete , comprehensive and finalized description and explanation of all of the very complex physical and chemical factors involved in the propagation of light through living tissue , nor for every meaningful aspect of the data obtained by the method and apparatus disclosed ; further , it is not intended to teach complete and definitive methodology for specific medical diagnosis . instead , it is intended to show highly useful methods and apparatus for clinical examination and study of human subjects , and for presentation of the data so achieved , including comparative presentations for similar positions on different but analogous body portions of the same patient , and for a broad cross section of different patients at both the same and different ages , and also with respect to particular patients at various different points in their lifespan . thus , while the invention contemplates the presence of clinically efficacious modalities which may be useful for many purposes perhaps including diagnosis of particular conditions and / or illness , it is presently contemplated that perhaps the most useful contribution of the invention is to provide a screening device and modality in which a familiar and therefore non - frightening medium ( i . e ., &# 34 ; light &# 34 ;) is utilized in a harmless and noninvasive procedure made possible by relatively inexpensive apparatus operable by medical technicians as opposed to physicians themselves , primarily useful for indicating the need ( or lack thereof ) for much more intensive analytical investigation , i . e ., mammography , ultrasound , biopsy , etc . in this respect , both the tabular - type form of data presentation and the graphical - type format are considered useful and , as already indicated , the tabular format may be made much more comprehensive and diverse than that set forth for purposes of illustration hereinabove . particular advantage is asserted with respect to the methodology involved in and epitomized by the graphical presentations of fig1 , however , particularly with respect to the use of the different data - taking positions , the nature of the graphical format , and the comparative ( paired ) presentation . it should be noted that the foregoing specification and appended drawings disclose concepts and methodologies principally described herein as applicable to study of the human female breast , but which are not at all limited to use for this purpose . that is , optical response and particularly spectral response data profiling in the manner described herein is definitely considered to be appropriate for , and valuable in , examination of other body portions , human or otherwise . while it may or may not be true that a given such application may call for slightly varying the specifics of the modality in actual application , the basic underlying concepts should nonetheless prove applicable and effective . accordingly , the scope of this patent should be determined by consideration of the appended claims rather than with respect to specific attributes or parameters set forth above and / or in the attached drawings , describing and illustrating various preferred embodiments or characteristics , the scope of the claims to be determined through appropriate application of established principles of patent law including the doctrine of equivalents .