THE HOOK WORM 



275 



The mouth cavity of the embryo is about as deep as the diameter 

 of the embryo at the posterior end of the mouth cavity; that of Strongy- 

 loides is only about one-half as deep as the diameter. 



A temperature of i C. kills the eggs in twenty- four to forty-eight hours. After 

 moulting twice, it remains rather quiescent but still lying inside the discarded skin. 

 It reaches this stage in from four to fourteen days according to the temperature. 



The soil in the area of the hookworm-egg-laden stool becomes infested with these 



FIG. 75. i a, Copulatory bursa of Necator americanus, showing the deep cleft 

 dividing the branches of the dorsal ray and the bipartite tips of the branches; also 

 showing the fusion of the spicules to terminate in a single barb. Scale i/io mm. 

 ib, Branches of dorsal ray magnified. 2a, The buccal capsule of N. americanus. 

 2b, The same magnified. 3a, Copulatory bursa of Ancylostoma duodenalc, showing 

 shallow clefts between branches of the dorsal ray and the tridigitate terminations. 

 Spicules hair-like. 3b, The dorsal ray magnified. 4a, The buccal capsule of A. 

 dnodcnale, showing the much larger mouth opening and the prominent hook-like 

 ventral teeth. 4b, the same magnified. $a, Egg of N. americanus. 5b, Egg of 

 A. duodenale. 6a, Rhabditiform larva of Strongyloides as seen in fresh faces. 

 6b, Rhabditiform larva of hookworm in faeces eight to twelve hours after passage 

 of stool. 



larvae which will even climb up blades of grass. It is for this reason that children with 

 their bare feet are so liable to infection. (If the larvae get into water they sink to the 

 bottom.) It is at this stage that it burrows into the skin of man, producing the so- 

 called "ground-itch " at the site of entrance. Having gained access to the lymphatics 

 and veins, they eventually reach the lungs. Here they get into the bronchioles and 



