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I XT EST IN A L SCHISTOSOMIASIS 257 



II CESTODA PATHOGENIC TO MAN (Human Tapeworms). 



(Kestos -= a girdle.) 



GENERAL REMARKS. 



Cestoda are Plalyhelmia which differ from Trematodes in that : — 

 (i) There is no alimentary system, the food being absorbed 

 through the cuticle. 



(2) There is a simple fixative apparatus at the anterior extremity 

 of the body. 



(3) The parasites are divided into segments, each segment being a 

 distinct hermaphrodite animal. 



(4) Thev are longer and flatter, varying from ^ to 24 inches long. 

 The adult inhabits the intestine, and the larval form usually in- 

 habits some other host. 



Every vital function is subordinate to the development of ova. 

 They have been known for centuries. 



Moses forbade the Israelites to eat pigs and similar animals because 

 parasites were then known to exist in them. 



Aristotle recognized the proglottides of tapeworms. 



MORPHOLOGY. 



Cestodaria with only one segment and not important. Cestoda 

 having a scolex and segments. 



We are concerned with these latter. 



The true cestodes have a tape-like whitish segmented body. 



The anterior end has a scolex attached to the intestinal wall, the 

 segments or proglottides follow and increase in size from the head 

 downwards. The head attaches itself to the mucous membrane of the 

 intestinal tract by means of muscular suckers. There may also be one 

 or more circular rows of hooks situated upon the most anterior part of 

 the head or rostrum. Each segment contains male and female sexual 

 organs. The thick cuticle contains lime salts in abundance. Among 

 the cellular elements are calcareous corpuscles, 3-30 /x in diameter, 

 which are characteristic of the cestodes, having perhaps a protective 

 or skeletal function. 



There is an outer layer of longitudinal and an inner of transverse 

 muscle fibre which encloses the parenchyma. 



There is an excretory svstem of anastomizing capillaries passing 

 into collecting tubules w^hich open to the exterior on the last proglottis. 



The nervous system consists of one ganglion and two nerve cords. 



The male generative organs reach maturity first. The vas deferens 

 from the follicular testes enters the cirrus pouch and terminates near 

 the vaginal orifice at the genital atrium. 



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