But  are  these  really  sources  of  infection,  or  are  they,  as  so
many  believe,  an  imaginary  danger  evolved  in  the  brain  of
the  laboratory  worker  ?  It  is  well  again  to  emphasize  the
fact  that  long  before  Klebs  and  Loeffler  identified  the  bacillus
of  this  disease  a  few  able  clinical  observers  like  Jacobi  be-
lieved that  evidence  pointed  clearly  to  the  great  danger  of
these  unrecognized  sources  of  infection.  The  bacteriologists
have  not  raised  the  bugaboo  of  carrier  infection,  they  have
simply  explained  the  facts  which  observing  men  have  long
recognized.
Carriers  cause  Disease.  —  A  little  perusal  of  medical  liter-
ature will  show  that  many  cases  are  reported  of  what  is
apparently  the  distribution  of  diphtheria  by  carriers.
Peck  9  reports  an  instance  where  a  young  man  who  was

1  Park,  Med.  Rec.,  N.  Y.,  1892,  XLII,  121.
2  Abbott,  Med.  News,  Phila.,  1893,  LXII,  505.
3  Ravenel,  Med.  News,  Phila.,  1895,  LXVI,  537.
4  Schaps,  Arch.  f.  Kinderh.,  Stuttg.,  1905,  XL,  80.
5  Treitel  and  Koppel,  Arch.  f.  Kinderh.,  Stuttg.,  1895-96,  XIX,  107.
6  DeStella,  Arch,  internat.  de  laryngol.  [etc.],  Par.,  1903,  XVI,  970.
7  Ballin,  Jahrb.  f.  Kinderh.,  1903,  LVIII,  412.
8  Newsholme,  Rep.  Med.  Off.  Health,  Brighton,  1906,  13;  Address  at
Victoria  Univ.,  Manchester,  March  9,  1904,  21.
9  Peck,  Brit  M.  J..  Lond.,  1895,  I,  971.
96          THE  SOURCES  AND  MODES  OF  INFECTION

perfectly  well  but  was  a  carrier,  probably  gave  diphtheria  to
another  young  man  with  whom  he  slept.
