706 MEDICAL ENTOMOLOGY 



Cyclops abounds in the tropics in all large and small collections of 

 fresh water ; many of the species are of special importance as they are 



the invertebrate hosts of the Guinea- worm, Dracunculus 

 Relation to Disease . 



medmensis. Fedscnenko, working in Turkestan, was 



the first to demonstrate that the embryos of the Guinea-worm undergo 

 some developmental change in the body of Cyclops, his observations 

 being confirmed later by Manson in England. Fedschenko believed 

 that when the dracunculus-infected Cyclops was ingested by man in 

 drinking water, the worm was liberated by the dissolution of the crustacean, 

 and that it then burrowed into the tissues of its new host, man, and 

 slowly became transformed into the well-known adult worm, which 

 appeared at the surface of the skin on the legs and feet ; this observer, 

 however, failed to infect man by means of infected Cyclops, and the 

 hypothesis remained sub judice. Leiper next attacked the problem, 

 and he was able to show that, when an infected Cyclops was placed in a 

 two per cent solution of hydrochloric acid, the crustacean was killed, but 

 the contained larva of Dracunculus was stimulated into great activity 

 and soon escaped from the body of its host. The obvious conclusion 

 was that the hydrochloric acid in the stomach of man or an animal 

 would have the same effect. In order to test the hypothesis Leiper fed 

 a monkey with a large number of Cyclops which had been infected six 

 weeks previously, and which were known to contain mature larvae of 

 the Guinea-worm ; six months later, when the monkey died, he found 

 in the connective tissue five worms, which resembled the adult Dra- 

 cunculus. This experiment has yet to be confirmed. 



According to Fedschenko the Guinea-worm embryo penetrates the 

 Cyclops by piercing it between the segments on the ventral surface, and 



Wenyon states that he has seen this phenomenon take 

 Development of D. , . . . , _ . _ . 



medinensis in Cyclops P lace ln hls experiments in the Soudan. Leiper, on 



the other hand, is of the opinion that the embryos 

 enter by way of the alimentary tract. Roubaud, in a recent paper, 

 records having experimentally confirmed Leiper's observations, and 

 maintains that the infection is intestinal. He placed a large number of 

 Cyclops in water which had been previously rendered cloudy with 

 embryos of D. medmensis, and found that six hours later many of the 

 Cyclops contained groups of embryos in the region of the mid-gut ; the 

 embryos were very active and did not appear to be affected by the 

 digestive juices of their host. In the fresh condition none of the 

 embryos were seen in the body cavity, but in sections of the host some 

 were seen lying in the body cavity close to the mid-intestine. Twenty- 



