THE TAPEWORM LARViE 203 



no recognizable symptoms, and, unless the cysts can be seen beneath 

 the visible mucous membranes, the condition is only observed post- 

 mortem. If the cysticerci become lodged in nerve centers, there may be 

 such manifestations as circling movements, grinding of the teeth, or, 

 possibly, convulsions and opisthotonos; symptoms which can no more 

 than suggest measles as a possible cause. 



Measles of the Sheep 



Taenia hydatigena, of which Cysticercus tenuicollis of the sheep is the 

 larval form, has been described under Cestodes of the Dog (p. 178). 



Occurrence. — Cysticercus tenuicollis has its development under serous 

 membranes of the sheep principally, but it may also appear in other 

 ruminants and in the pig. Infestatiori is by food and water bearing 

 ova which have been spread about by dogs harboring the adult worm. 



Experiments have shown that the majority of the embryos reach the 

 peritoneal cavity by way of the liver. Ten days after infestation tor- 

 tuous hemorrhagic trails may be found upon the surface of this organ 

 under the capsule of Ghsson. These are produced by the migrations of 

 the parasites, and are in close relation, usually at their extremities, with 

 vesicles 0.5-3.5 mm. in diameter. The head is fully developed about 

 the fortieth day, and the vesicle reaches its full growth at about the 

 seventh month, when it may have a diameter of 1.5-5 cm. (5/8-2 inches), 

 often about the size and form of a pigeon'g egg. 



These cysts ("water-balls") may be fotind in varying numbers, their 

 size and location depending upon the age of the infestation. Their 

 seat, especially in young animals, is usually beneath the serous capsule 

 of the Hver, though, particularly in old infestations, large bladders may 

 be foimd in most any part of the peritoneal cavity. 



As it relates to food sanitation, this cysticercus of sheep is of little 

 importance. The location and size of the cysts render them easy of 

 elimination from parts used as human food. 



As a matter of control, it is obvious, in reference to the life history of 

 the tapeworm, that offal containing such cysts should be inaccessible 

 to dogs. 



Symptoms. — Sheep measles can rarely be recognized until after the 

 death of the animal. 



Cysticercus ovis. — Muscular cysticercosis in sheep has been shown 

 by investigations within the past few years to be more common than 

 had been suspected. It has been determined by Ransom that the 

 cysticercus is derived from a tapeworm having its adult development in 

 the dog, and not to a tapeworm of man as had been supposed. 



The following data in regard to this form of measles are quoted from 

 Hall (Bulletin No. 260, U. S. Dept. of Agriculture): 



