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. 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 prac- 

 tically all cases of elephantiasis in the Welle 

 district of Congo, where Filaria bancrofti is said 

 not to occur, are accompanied by infection 

 with Onchocerca volvulus. Recently Robles 

 has described Onchocerca ccecutiens causing 

 subcutaneous nodules on the heads of natives 

 in parts of Guatemala, and suspects certain 

 species of Simulium as carriers. 



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 FIG. 130. Guinea- 

 " fiery serpents " which molested the Israelites ^zj^^ 

 by the Red Sea and were mentioned by Moses Natural size. (After 

 were probably guinea- worms. These parasites Leuckart -) 

 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, 



