THE MICROSCOPE IN AETIOLOGY. 333 



intestine. Develops to from two to three meters long, and 

 its proglottides ten mm. long and six mm. broad. Head 

 the size of a pin, globular, with tolerably prominent suck- 

 ers. Filamentous neck, almost an inch long. The cyst worm 

 (Cysticercus celluloses] of this species has a preference for 

 the muscles of the hog, but is found in other animals and 

 in man. 



2. Tee nia Mediocanellata. Larger than the T. solium. 

 Head without a circle of hooks and rostellum, but with 

 powerful suckers. The cystworm inhabits the muscles of 

 cattle, but has not been found in man. 



3. T. Acanthotrias. The vesicle only is known. Found 

 in muscles, subcutaneous tissue, and brain of man. Hook 

 apparatus a triple circle of slender claws. 



4. T. Marginata. Mature tsenioe are like T. solium, but 

 found in the dog and wolf. The larva abides in the 

 omentum or liver of ruminants and swine, and sometimes 

 of man. One extremity of the vesicle is drawn out in a 

 necklike process, which contains the tapeworm. 



b. Cyst tapeworms, whose heads bud from the embry- 

 onic capsules of the inner surface of 'the vesicle. 



5. Tcenia echinococcus consists of only three or four seg- 

 ments, the last of which exceeds in bulk all the others. 

 It is three to four mm. long, and its thirty or forty hook- 

 lets are on a prominent rostellum. It lives in the intes- 

 tine of the dog. The young state of this Tsenia (echino- 

 coccus) is an almost motionless vesicle on the inner sur- 

 face, of which numerous little heads bud in vesicles the 

 size of a millet-seed. These are sometimes compound 

 (daughter, granddaughter vesicles\ inclosed one within the 

 other. In this form they are found in man and cattle 

 (especially in the liver). Other animals harbor generally 

 single vesicles. 



B. Common tapeworms, Cystoidece. They represent no 

 peculiar larv?e. Their larvae occur only in cold-blooded 

 animals or invertebrates. Thus the cysticercoid of T. 



