388 



THE ANIMAL PARASITES OF MAN 



of the body and produces there a thickening as big as a florin. Over 

 this a vesicle forms which eventually ruptures, and at the bottom 

 of the ulcer can be seen a hole from which a part of the worm may 

 project. On bathing the sides of the ulcer with water, a drop of 

 fluid, at first clear then milky, exudes. This contains numerous larvae. 

 In other cases a thin tube an inch long is prolapsed (through the 

 vulva). This is probably the uterus, but the mechanism of parturition 

 is not clearly known. It lasts for about a fortnight. An abundant 

 supply of larvae can be got by placing wet compresses on a fresh 

 ulcer. In a few hours a mass of larvae is obtained. 



The larvae are 500 ^ to 750 //, by 15/4 to 25^, with a long slender 

 tail about one-third of the total length. The cuticle is transversely 

 striated. The body is flattened. They possess an oesophagus and 

 gut. At the anus there are apparently glandular structures. 



The larvae live 

 and move actively in 

 water for about two 

 days, the majority 

 dying on the third 

 (Leiper). If a num- 

 ber of Cyclops sp. 

 have been collected 

 and isolated in clean 

 water, and the larvae 

 are now added, the 

 further development 

 can be traced. 



The larvae enter 

 the Cyclops, accord- 

 ing to most authori- 

 ties, by penetrating 

 the exoskeleton, but 

 according to Leiper this is impossible ; they must enter by the mouth 

 and penetrate the gut in order to reach the body cavity. In eight days 

 moult i takes place, the striated cuticle being cast off. In ten days 

 moult 2 takes place. In five weeks the larva is mature. If now the 

 infected Cyclops is placed in o'2 per cent. HC1 solution the Cyclops is 

 killed immediately, but the larvae are stirred into activity, escape from 

 the body, and swim about in the acid. This suggests that infection 

 in nature probably takes place by the swallowing of infected Cyclops ; 

 Leiper, by feeding Cyclops containing mature larvae to a monkey, found 

 in it, post mortem six months later, two immature females 30 cm. long 

 and two males 22 mm. long. 



In certain areas the new cases occur principally in June. Five 



FIG. 279. Transverse section of female Guinea worm : 

 u., uterus containing embryos ; i., intestinal canal ; o. y ovary. 

 (After Leuckart.) 



