taste  fibres  from  the  glossopharyngeal  by  the  connection  between  the  large
and  small  petrosal  nerves  (see  p.  642).  The  fact  of  most  weight  connecting
the  function  of  taste  with  the  glosso-pharyngeal  is  that  its  fibres  have  been
traced  to  the  circumvallate  papillae,  the  nerve  structures  in  which,  believed
to  subserve  taste,  undergo  degenerative  changes  after  division  of  the  nerve
trunk.  On  the  other  hand,  there  is  no  instance  on  record  of  loss  of  taste  at
the  back  of  the  tongue  from  disease  of  the  roots  of  the  glosso-pharyngeal
nerve,  while  there  is  evidence,  as  mentioned  on  p.  642,  that  disease  of  the
root  of  the  fifth  nerve  causes  loss  of  taste  on  the  back  as  well  as  the  front  of
the  tongue,  and  also  on  the  palate  and  palatine  arch.  Hence  it  is  difficult
to  resist  the  conclusion  that  if  some  of  the  terminal  fibres  of  the  glosso-
pharyngeal nerve  subserve  taste,  such  fibres  come  ultimately  from  the  fifth
nerve.  Their  path  must  then  be  from  the  otic  ganglion,  through  the  tym-
panic plexus,  to  the  petrous  ganglion  of  the  glosso-pharyngeal,  a  circuitous
path,  but  scarcely  more  so  than  that  which  the  taste  fibres  of  the  chorda
tympani  undoubtedly  take.  This  view  is  supported  by  the  fact  (mentioned
on  p.  643)  that  taste  on  the  back  of  the  tongue  may  be  lost  in  disease  of  the
middle  ear,  a  fact  explicable  on  no  other  hypothesis.
