824 Measles. 



blood stream into different organs but especially into the muscular 

 tissue. The onkospheres noAv change into simple vesicles or cysts, on 

 whose wall small nodules arise later, and from these the heads of the 

 future tapeworms develop. 



The development occurs rather slowly. In 20 days the Cysticercus cellulosse 

 is about the size of a pinhead and the head is visible as a small white point; after 

 40 days it appears as Ing as a mustard seed and the head may be plainly seen, but 

 it has neither suckers nor hooks; after 60 days the cyst is as big as a pea, with 

 suckers and hooks but no neck; after 3 months the bladder worm is fully developed 

 and liehind the scolex the transversely striped neck may be seen (Hosier). The 

 growth of Cysticercus bovis occurs still more slowly. After 60 days the head appears 

 as large as a pinhead with plainly visible suckers; the visible depression at the 

 anterior end of the head develops in the sixth month, when the cyst has already 

 reached the size of a small bean, but later it develops further and grows to a length 

 of 12 mm. Hoefnagel & Reeser found cysticerci, 5 mm. in length, after 45 days, in 

 a calf used for experimental infection. 



Natural infection occurs by food or water wliicli is con- 

 taminated by human feces containing the proglottides or liber- 

 ated eggs, and is eaten by animals. Swane are attacked especial- 

 ly easily because tliey root about in dung heaps and in the neigh- 

 borhood of latrines and sewage deposits, and because they root 

 up soiled earth. Consequently the disease frequently occurs 

 in such swine as move about freely in peasants' yards or in 

 the neighborhood of sties Iniilt near dw^elling houses, while the 

 large herds which are mostly kept in a state of freedom are 

 seldom attacked. The infection in cattle probably results pri- 

 marily from food or drinking water contaminated by human 

 fecal matter, but it is not eliminated on pastures if persons 

 with tapeworm deposit their feces there, or if during floods the 

 contents of canals have been carried to the pastures. Contami- 

 nation of the drinking water is easy, as brooks frequently are 

 found in the immediate neighborhood of latrines or manure 

 heaps. It is also to be considered that eggs of the tapeworm 

 are viable on damp ground for a very long time, and conse- 

 quently even one infested man may infect the ground for a long 

 time with the enormous number of deposited eggs (one prog- 

 lottis contains about 30,000 eggs), (van Beneden found that 

 eggs kept by him in alcohol for a year could still develop em- 

 bryos.) 



Susceptibility. Young animals under 2 years of age are 

 especially susceptible. The disease does not occur in sucking 

 animals, because generally no opportunity occurs for infection. 

 Exceptionally, however, quite young animals fall ill; thus 

 Deleidi and Noack found some ca seated cysticerci in sucking 

 calves under t^vo months old and these must have been taken 

 up shortly after birth. In these cases it was supposed that 

 the infection had been caused through hens' eggs given to the 

 calves by an attendant affected with tapeworm, whose hands 

 were soiled. In older animals the toughness of the tissues is 

 much less favorable for the migration and further growth of 

 onkospheres. 



