2l6 



THE ANIMAL PARASITES OF MAN 



brane, sinks to the bottom and is capable of a creeping motion ; 

 sooner or later it dies in the water. The manner and means of 

 its invasion of an intermediary host is still unknown ; yet we are 

 aware that the cysticercus stage (plerocercoid, fig. 144), which 

 resembles the scolex and may reach a length of 30 mm., lives in 

 the intestine, in the intestinal wall, in the liver, spleen, generative 

 glands and muscular system of various fresh water fishes (fig. 145), 

 the pike (Esox Indus), the miller's thumb (Lota vulgaris), the perch 

 (Perca fluviatilis), Salmo umbla, Trutta vulgaris, Tr. lacustris, Thymallis 

 vulgaris, Coregonus lavaretus, C. albula and Onchorhynchus perryi. 

 The transmission of the plerocercoids from these fish to the dog, cat 

 and man (Braun, Parona, Grassi and Ferrara, Grassi and Rovelli, 



FIG. 142. Free-swimming on co- 

 sphere of Dibothrincephalus latus. 

 (After Schauinsland.) 



FIG. 143. Free-swimming on- 

 cosphere of DibothyiocepJialus 

 latus. SOO/T. Distinct muscular 

 fibres are seen in addition to the 

 three pairs of booklets. (After 

 Leuckart.) 



Ijima, Zschokke, Schroeder) leads to the development of the broad 

 tapeworm, the growth of which is rapid. In my experiments on 

 human beings the average number of proglottides formed per diem 

 averaged 31 to 32 for five weeks, with a length of 8 9 cm. Accord- 

 ing to Parona the eggs appear soon after the man has been 

 infected (twenty-four days)., Zschokke found the average growth 

 in the experimental infection of man between 5*2 and 8*2 cm. 

 per diem, and the person experimented upon by Ijima evacuated 

 a piece of a Dibothriocephalus latus, 22*5 cm. in length, only 

 twenty-one days after the infection. 



The " broad tapeworm " is a frequent pajrasite of man in 

 some districts, but it also occurs in the domestic dog, and on rare 



