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 microfilariae. The latter are 

 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 

 filariae, is the guinea-worm, Dracunculus medi- 

 nensis (Fig. 130). This is 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 Israehtes 

 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, 



Fig. 130. Guinea^ 

 w o r m, Dracunculus 

 medinensis, female. 

 Natural size. (After 

 Leuckart.) 



