The  number  of  genera  is  about  eighty.  Cer-
tain species  in  the  adult,  sexually  ripe  stage
infest  the  small  intestine  of  man — the  definitive
host;  the  corresponding  larval  forms  live  normally
in  the  intramuscular  connective  tissue  and  viscera
of  certain  animals  which  constitute  the  interme-
diate host.  Exceptionally  man,  by  swallowing
the  embryos — oncospheres — becomes  the  host  of
the  larval  forms — Cysticcrcus  celluloaa;;  Echino-
coccus.    The  most  common  tapeworms  of  man  arc:

(a)  Tienia  Solium  (Armed  Tapeworm;  Pork
Tapev'orm). — This  cestode  was  so  called  because
it  was  supposed  to  exist  as  a  solitary  parasite  in
the  intestine.  It  ia  now  known  that  two  or  more
tapeworma  may  be  present  at  the  same  time.
Average  length  3  metres;  head  globular,
0.8-1.0  mm.  in  diameter  and  armed  with  a  3
double  row  of  hooks;  suckers  hemispherical;  neck
slender  and  5-10  mm.  in  length;  proglottides  800-1000  in  number  when
mature  and  ready  for  detachment,  10-12  mm.  in  length  by  5-6  mm.  in
breadth;  genital  pores  alternate;  uterus  consists  of  a  median  trunk  with
7-10  lateral  branches  on  each  side,  some  of  which  again  branch;  eggs  oval
with  very  delicate  ?hell;  embryonal  shell  thick,  globular,  of  a  pale  yellow-
ish color  with  radial  stripes,  0.031-0.036  mm.  in  diameter;  the  embryo
armed  with  six  hooklets.  This  parasite  when  fully  developed  is  found
exclusively  in  the  small  intestine  of  man.  The  embryos  are  voided  with
the  ffficcs  hut  undergo  no  further  development  unless  taken  into  the  stom-


MEDICAL  DIAGNOSIS.
ach  of  a  aiiitable  animal,  especially  the  hog  or  man  himself.  The  embryo
shells  arc  then  digested,  the  armed  embryos  are  set  free,  and,  finding  their
way  to  various  parts  of  the  body,  develop  into  the  larvic  or  cysticerci.
