Flatworms and Threadworms 



305 



Fig. 192. Elephantiasis in Man 



(From "New Sydenham 



Society's Atlas.") 



The writer has been told by a worker in 

 the medical corps of the army that more than 

 75 per cent of the examined southern negroes 

 showed hookworm infection. 



It is of great importance to dispose of all 

 human faeces in rural districts, in mines, brick- 

 yards, etc., so that the soil will not become 

 polluted. This will at the same time kill, the 

 eggs and thus prevent their hatching. Strong 

 sunlight also seems to be quite effective in 

 killing such eggs. 



The family Filariidae is also important 

 from a pathological point of view. 



Filaria bancrofti (Fig. 191) is a parasite 

 which lives in human blood. It is interesting 

 to know that this parasite lives in the lungs 

 and larger arteries throughout the day and in the blood vessels in the 

 skin at night. Mosquitoes, which are active at night, suck the blood of 

 infected persons and thus carry the infection. In fact, it was the knowl- 

 edge of this peculiarity of Filaria bancrofti which led to the discovery 

 of the malarial parasite's life cycle. 



After the larvae have developed in the mosquito's body, the 

 organisms are placed in another person by the mosquito. They enter the 

 lymphatics and cause serious difficulties, probably by blocking the lymph 

 passage. If there is such a blocking, elephantiasis results. This is a 

 practically incurable disease in which the limbs, or other portions of the 

 body, swell to an enormous size, although producing little or no pain. 

 (Fig. 192.) In certain portions of the South Sea Islands, almost a third 

 of the population is affected. 



Medical men speak of Filaria diurna and Filaria perstans. The first 

 of these differs from F. bancrofti in not having granules in the axis of 

 the body, and the second in having embryos smaller (namely, about 

 200 microns) than the preceding. Only the embryos have been seen. 

 The embryos of F. bancrofti are about 270 to 340 microns in length. 

 The adult is about 83 mm. long, and the female some 155 mm. The tail 

 in the male has two spiral turns. The female produces vast numbers 

 of young which enter the blood stream through the lymphatics. Each 

 embryo is inclosed in a tiny shell, about one ninetieth of an inch in 

 length. They pass through the capillaries quite readily. They can be 

 seen in a blooddrop under the microscope. As many as 2,100 embryos 

 have been seen in 1 cc. of blood. 



Dracunculus medinensis is a peculiar worm, the female of which is 

 about a yard long. It is probably taken in with food. It makes its way 

 downward, and, when arriving at the ankle, usually pushes its head 

 through the skin, causing an abscess. As the eggs are then deposited, it 



