CESTODA 



37 



In England the annual loss of sheep killed by the liver-flukes is estimated 

 at $1,000,000, and it has been known to reach $3,000,000 in one year. 

 There have been a few cases of this parasite found in man. 



CLASS HI. CESTODA 



A tapeworm (Tce'nia so'lium) is a parasite in the intestine 

 of man. It is ribbon shaped (Fig. 27), being much narrower at 

 the attached end, the head, or scolex. 



The scolex is knob-shaped and bears the organs of attach- 

 ment, a circle of hooks at the end, and a sucking disk or cup- 

 shaped sucker on each of the four sides. The attachment is 

 temporary. 



Fig. 27. Tce'nia sagina'ta. (Eichhorst.) 



Segments. The remainder of the tapeworm, except a short 

 portion immediately posterior to the head, is made up of a series 

 of segments or proglottides, the number of which varies in differ- 

 ent species. In Tsenia solium there are about eight hundred and 

 fifty segments, while in the smaller species there are three or four 

 hundred, and in the larger species, several thousand. These 

 segments or proglottides are derived from the head by a kind 

 of budding. Thus it is that so long as the head remains the 

 tapeworm continues to grow. 



Digestion. There is no digestive system, the nutrition 

 simply being absorbed from the liquids of the host. 



The nervous system consists of a pair of ganglia, from which 

 two main nerve-cords extend back through the length of the 

 worm. 



The excretory or water-vascular system consists usually of 



