202 PARASITES OF THE DOMESTIC ANIMALS 



three in a piece of meat weighing seventeen grammes (260 gr.), — propor- 

 tionately eight thousand per kilogramme (2 lbs). 



More delicate and transparent than those of beef measles, the cysts 

 are elliptical in form, 6-15 mm. long by 5-10 mm. broad (1/4-5/8 by 

 7/32-3/8 of an inch). The wall enveloping the vesicle is a thin semi- 

 transparent connective tissue membrane which, in loose connection with 

 the surrounding tissue, when removed, leaves a reddened alveolar pit. 

 Pressure upon the caudal vesicle causes the evagination of the larval 

 head which, on examination by low magnification, is seen to be te- 

 tragonal and to possess, in addition to the four suckers, a double crown 

 of twenty-two to thirty hooks, — characters defining it as the larval 

 head of Tcenia solium. 



At about twenty days from infestation the cyst shows as a delicate 

 vesicle about the size of a pin head, with the rudimentary head indicated 

 by a cloudy point, and as yet without enveloping connective tissue mem- 

 brane. At the age of one hundred and ten days all of the cysts are 

 approximately of equal size; the scolex is developed and lies invaginated 

 into the caudal bladder. When located in organs such as the lungs, 

 liver, and spleen, they often appear as grayish, caseous, calcareous, or 

 purulent nodules somewhat resembling those of tuberculosis. Differen- 

 tiation can be made by careful examination which will reveal the hooks 

 and often the larval heads. 



In some cases a diagnosis can be made while the animal is still living 

 by examination of the inferior surface of the tongue. If cysts are present 

 in that organ, they will be near the base and at the sides of the frsenum, 

 where they may be seen as semi-transparent, round or oval vesicles 

 protruding beneath the mucous membrane. 



Degeneration. — Degeneration of the cysts may begin at any stage 

 of their development, though those in the visceral organs are the first to 

 undergo these changes. The process begins with the connective tissue 

 envelop and later involves the scolex. The caseous cysts present a 

 gray color, while those which have become calcified are white. In the 

 older degenerated cysts the changes have advanced to transformation 

 into small calcareous bodies without fluid, constituting the "dry 

 measles " as termed by the butcher. In such cases the larvae are un- 

 doubtedly dead. 



Vitality. — The cysticercus of pork measles is slightly more resistant 

 to heat than is that of beef measles. Under post-mortem conditions it 

 survives much longer. Ostertag found living larva; in pork forty-two 

 days after it had been slaughtered. Preservation in cold storage as for 

 beef measles, therefore, will not be effectual. All cysts will be rendered 

 harmless if the pork is cooked until its cut surface presents a uniformly 

 whitish color. 



Symptoms. — Ordinarily measles of the pig, as in the ox, presents 



