The  last  molar  tooth  is  a  guide  to  the  introduction  of  a  tube  into  the
mouth,  in  case  of  tetanic  fixation  of  the  jaw  requiring  forced  alimenta-
tion, since  a  space  exists  between  that  tooth  and  the  ramus  of  the  jaw
sufficiently  large  to  admit  a  tube  of  moderate  size.
The  cavity  of  the  superior  maxillary  bone  (the  antrum '  or  "  maxillary
sinus")  is  the  frequent  seat  of  disease.  Within  it2  may  be  developed
either  solid  or  cystic  tumors,  and  pus  not  infrequently  accumulates.  The
close  relation  of  the  different  walls  of  this  cavity  to  important  structures
gives  to  these  growths  more  than  a  passing  interest.
If  the  inner  wall  becomes  expanded,  the  nostril  may  be  occluded  ;  if
the  lower  wall,  the  roof  of  the  mouth  may  be  depressed;  while  the  inferior
maxillary  nerve,  which  runs  above  it,  may  be  pressed  upon  if  the  upper
wall  is  affected,  and  the  orbit  may  furthermore  be  so  encroached  upon
as  to  greatly  displace  the  eye.  If  the  posterior  wall  be  crowded  back-
ward, the  zygomatic  fossa  will  be  encroached  upon,  and  tumors  have  thus
created  a  marked  swelling  in  the  region  of  the  temple.3  Finally,  the  an-
terior wall  may  become  prominent,  and  thus  greatly  distort  and  disfigure
that  side  of  the  face.
