196 PARASITES IN THE INTESTINES 



of hares and rabbits. Dogs become infested by eating the 

 viscera and in twelve days the taeniae are 2 to 3 cm. long, and 

 matured in two months. The ripe ova given to rabbits 

 become cysticerci. 



(c) Twnia hydatigena (Taenia marginata).— This is the 

 largest taenia found in the dog, being 1.5 to 2.0 m. long. 

 The head is scarcely wider than the neck and has 30 to 44 

 hooks. The segments are nearly square with the genital pore 

 on the lateral border which begins to develop in the seg- 

 ments about one-fourth of the distance from the head. The 

 posterior border of the segments is slightly wavy, and 

 received into the succeeding segment. Mature segments 

 when detached are about 15 mm. long by 7 mm. wide. The 

 ova are almost spherical and from 30 to 36 microns in 

 diameter. The cyst form is the Cysticercus tenuicollis and 

 is commonly found in the peritoneum, pleura and even in the 

 pericardium of domesticated animals, especially ruminants. 

 It requires four to five months to fully develop into the mature 

 worm. 



(d) Multiceps multiceps (Twnia cwnurus). — This worm 

 rarely exceeds 1 m. in length. Head small, slightly broader 

 than the neck and armed with 22 to 32 hooks. Segments 

 narrower than any of the preceding species, becoming square 

 with the genital pore developed about the 125th segment, 15 

 to 20 cm. from the head. Mature segments 10 to 12 m. 

 long, 3 to 4 m. wide. Eggs spherical 31 to 36 microns in 

 diameter. The cystic form is the Multiceps multiceps 

 (Ccenurus cerebralis) which is developed in the cerebro- 

 spinal cavity of sheep; more rarely in other domesticated 

 animals, causing the disease commonly called "gid." The 

 cyst is polycephalic, the ingestion of one cyst producing 

 numerous taeniae. The taenia requires about two to three 

 months to reach maturity. 



(e) Multiceps serialis (Twnia serialis).— This parasite is 

 45 to 75 cm. long, head wider than the neck and having 

 26 to 32 hooks. Segments similar to those of the M. multi- 

 ceps. The ripe segments are 10 to 16 mm. long and 3 to 4 

 mm. wide, the posterior border being straight. Eggs ovoid 

 and 34 microns long and 27 microns wide. The cyst form is 



