GUINEA-WORM 



311 



sides of the chest and upper part of the back, and sometimes 



in the arm and knee pits and on other parts of the body. Each 



swelling consists of dense fibrous tissue in which several pairs of 



parasites are imbedded, and contains small cystlike spaces into 



which project the posterior end of the male 



with its copulatory organs, and the anterior 



end of the female with its vaginal opening. 



These cystlike spaces are usually swarming 



with sheathless microfilarise. The latter arc 



believed by some authors to leave the tumors 



and to find their way ultimately to the blood- 

 vessels, whence they can be liberated by some 



blood-sucking insect. However, attempts to 



find them in the circulating blood practically 



always fail, though the larvse can usually be 



obtained easily from lymph glands in the groin. 



The intermediate host is unknown, but the 



stable-flies, Stomoxys, and tsetse flies, Glossina, 



have been suspected. The tumors are of long 



duration in man, and in some adults are said 



to have been present since childhood. It is 



significant that practically all cases of elephan- 

 tiasis in the Welle district of Congo, where 



Filaria bancrofti is said not to occur, are 



accompanied by infection with Onchocerca 

 -volvulus. 

 ^^—-^ The Guinea-worm. — Another connective 



tissue parasite, more distantly related to the 



filarise, Js the guinea-worm, Dracunculus medi- 



nensis (Fig. 130). Jihiajs a frequent parasite 



in many parts of tropical Asia and Africa and 



has been known for a very long time. The 



" fiery serpents " which molested the Israelites 



by the Red Sea and were mentioned by 



Moses were probably guinea-worms. These 



parasites creep in the deeper layers of the subcutaneous tissue 



where they can be more readily felt than seen, but the females 



always come to the surface of the skin to give birth to the myriads 



of wriggling young. 



The adult female worm, which is the only sex certainly known, 



P'iG. 130. Guinea- 

 worm, Dracunculus 

 m edinensis , female. 

 Natural size. (After 

 Leuckart.) 



