196 



PARASITES OF THE DOMESTIC ANBIALS 



long and narrower than the head. The segments, which may nmnber 

 from one thousand to one thousand three hundred or more, are at first 

 much wider than long. The complete development of the generative 

 organs occurs at about the six hundredth segment, at which location 

 the segments are about as long as broad. Segments containing the 

 mature embryos reach a length of 15-20 mm. (5/8-3/4 of an inch) and a 

 breadth of 5-7 mm. (1/4 -5/16 of an inch). The distal margin of each 

 segment is somewhat swollen and surrounds the base of the following 

 segment. The genital pores are irregularly alternate and protrude from 

 the margins more and more markedl}' as the segments approach the 

 distal end of the chain. The median trunk of the gravid uterus has 

 twenty to thirtj'-five delicate lateral branches on each side, and these 

 give off shorter secondary branches. 



The length of the entire chain may be from 3 to 12 meters (9-38 feet), 

 or it may reach a much greater length. 



Fig. 106. — Taenia saginata, portions of adult, — natural size (after Boas, by Kirkaldy 

 and Pollard, from Leuckart). 



The eggs (Fig. 110) are more or less globular, the shell frequently 

 carrying one or two filaments. As found in the feces, the eggs often 

 have the outer shell absent. 



Next to a small species — Hymenolepis nana — this is the most common 

 tapeworm of man in the United States, and, in fact, with the exception 

 of Diphyllohothrium latum in a few districts, is the most prevalent 

 species infesting man in other parts of the world. It is not found 

 adult in other animals, and its cysticercus lives almost exclusively in 

 the ox. 



Occurrence of Beef Measles. — That the beef tapeworm and its cj-sts 

 (Cysticercus bovis) are more commonl}^ met with in the United States 

 than the pork tapeworms is probably due to the fact that beef is more 

 often eaten rare in this countrj- than is pork. Beef measles, therefore, 

 is, in its relation to food sanitation, of the greater importance. Estimates 

 made upon cattle slaughtered under Federal inspection indicate that 

 nearly one per cent, of all the cattle slaughtered in the United States 



