3i6 DISEASES DUE TO HELMINTHS 



The female, 12 to 13 mm. long, has the vulva at the junction of 

 the middle and hinder parts of the body, so that when copulation 

 takes place the worm looks like the Greek letter gamma 7. 



LIFE-HISTORY. 



The adults live in the jejunum, where the females lay their eggs. 

 These eggs are colourless, with a thin, plain double shell, the cellular 

 contents being separated from the shell b)- a clear space. During its 

 passage through the intestine the cellular mass divides into two, then 

 four parts, and is usually seen in this form in the faeces. With 

 sufficient air, water and heat the embryo forms in twenty-four hours, 

 escapes from the shell, and begins to feed on faecal material. Larvae 

 measure from 200 to 250 fi by 15 to 17 /a. 



Ecdysis is completed in four to six days in the tropics; the larvae 

 then ceases to grow. It can remain alive in this condition for months, 

 living on the food in its own cells. The larva may be quite active, 

 swimming or climbing to any other suitable place. 



It enters the hair follicles of man, causing " ground itch," and may 

 even penetrate gloves, paper and boots in order to reach the skin. 

 Thence it passes to the lymphatics and venous blood-vessels. Some 

 of them reach the right heart and the lungs, whence they pass from 

 the capillaries to the alveoli along the bronchioles, bronchi, trachea 

 and larynx to the oesophagus, stomach and intestines, where they 

 remain. This occupies from seven to ten days, during which time 

 several ecdyses take place. In eight days these larvae, 3 to 5 mm. 

 long, attain maturity. In fourteen to sixteen days copulation has taken 

 place, and the eggs are seen in the fccces. 



The whole cycle takes eight to ten weeks. 



Sambon says that when the larv^ are in the lungs they pass from 

 the pulmonary capillaries to the pulmonary veins into the general 

 blood-stream, and hence into the mucosa of the jejunum, which they 

 pierce, and so enter the lumen of the bowel. 



He believes that those seen by Loos in the respiratory tract are 

 stray ones. Perhaps both are correct, but experience has shown that 

 the great majority pass as Loos has described. Some may enter 

 directly by the mouth, as when miners eat their food with soiled hands. 



In order to grow the larvse, place a thin layer of fseces in a Petri 

 dish and a piece of moistend blotting-paper on the top. The worms 

 will grow in two to three days and come upon the top of the blotting- 

 paper, where they can be well examined. 



Keep the paper moist ; later breathe on the paper ; this will 

 stimulate movement. 



For mounting them, embed in gh'cerin and egg-white smear, treat 



