EXAMINATION OF CYSTICEECOID STAGES 



155 



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1 to 2 cm. in length. They lie in the sexual glands, the liver, 

 the mesentery, and under the peritoneal coverings of the intestine. 

 They will also be found in the muscular structure, if this is cut with 

 a broad knife tangentially into thin slices, and these slices are held 

 either up to the light or over a dark background. The Pleuracoids 

 are generally enclosed in thin-walled cysts, though " wandering " 

 individuals are sometimes met with. The head is furnished with two 

 suckers and is always invaginated. It will be projected, however, 

 and the parasites will move actively about, if they are put into normal 

 saline solution at mammalian body temperature. 1 



A certain number of the 

 Cestodes of the domestic 

 mammals approximate in 

 their development to that 

 of T. solium, L., the arche- 

 type of the genus Tcenia. 

 These are T. crassicollis, 

 Eud., of cats ; T. serrata, 

 Gze.;T.marginata, Batsch ; 

 T. coenurusj Kuchenm. ; 

 and T. echinococcus, v. 

 Sieb., of dogs. To these 

 may be added T. serialis, 

 Baill., which occurs in dogs 

 in France, and probably 

 also in Russia, though not 

 in Germany; T. krabbei, 

 Moniez, which is parasitic, 

 probably in dogs, in 

 northern latitudes ; and 

 certain varieties observed 

 in wild mammals. The 

 group is characterized 

 by a homogeneous or- 

 ganization, and the specific distinctions are : the number, shape, 

 and size of the rostellar hooks ; the position, in ripe segments, of the 

 uterus ; and certain minor features not to be described here. All 

 the members of the group pass through a bladder-worm stage of 

 development, which is termed variously : " Cysticercus " of T. crassi- 

 collis, serrata, marginata, and krabbei ; " Coenurus " of T. ccenurus and 





FIG. 76. Portion of the germinal layer from 

 Echinococcus veterinorum spread out and viewed 

 from the under side. Single brood-capsules with 

 scolices, which are developed both inwards and 

 outwards. 50 : 1. 



1 When handling fish infected with Pleuracoids, or the flesh of cattle and swine 

 infected with Cysticerci, great caution should be observed. Self-infection may result 

 from the contact of the fingers with stray Cysticerci or Pleuracoids. 



