STRONGYLOIDES STERCORALIS 



629 



tlmlis) — but Leuckart showed that they were but succeeding stages 

 of one life-cycle. It is found in Europe, Africa, India, Ceylon, 

 Indo-China, China, the Philippines, Oceania, the United States, 

 the West Indies, and Brazil. 



The fully-developed worm is found in the duodenum and jejunum, 

 into the mucosa of which it has bored its way deeply. 



Morphology. — The parasitic adult worm is very small — 2*2 millimetres 

 long and 34 broad — with a finely striated cuticle, and a mouth surrounded 

 by four lips, leading into a cylindrical oesophagus, equal in length to one- 

 quarter of the whole body. The anus is just in front of 

 the tip of the tail. Inside this parasite can be seen ellip- 

 soidal eggs. The sex of this parasite is doubtful. Is it a 

 hermaphrodite, in which the male organs, after serving 

 their purpose, have degenerated, or is it a parthenogenetic 

 female ? At present these questions cannot be answered 

 definitely. Most probably it is a hermaphrodite. The 

 eggs measure 50 to 58 ^ in length by 30 to 34 in breadth, 

 and are arranged in strings surrounded by a delicate 

 tubular structure. They occur in the faeces only during 

 attacks of diarrhoea. 



Life-History.— The eggs are oviposited into the 

 mucosa of the host's intestine, and the embryos 

 hatch and find their way into the lumen, and are 

 evacuated with the faeces. On reaching water or 

 moist earth these embryos grow into adult male 

 and female forms, which coni negate, and then the ^ ^ -d „ 



r IT T-x, J j: r • FiG. 267. RhAB- 



female lays eggs. The eggs produce free-hvmg d i t i f d r m 

 rhabditif orm embryos, which moult and turn into Embryo of 

 filariform embryos, which have been shown by Strongyloides 

 Mozocchi and van Durne to penetrate the skin, b^^va^y^*^ as 

 not through the hair-follicles, but through the found i^n 

 horny layer into the rete Malpighii, and so into Human F^ces. 

 the corium. The experiments of Fiilleborn and (After Looss.) 

 V. Schilling-Torgau in infecting tracheotomized 

 dogs or dogs with the oesophagus cut and fixed to the skin with 

 larvae of Strongyloides stercoralis Bavay, 1877, have shown that 

 the more important route is from the skin to the lungs and so via 

 the trachea and oesophagus to the bowels, while a less important 

 route from the skin via the blood-stream directly to the bowel 

 can also take place (vide the life-history of Ancylostonta duodenale, 

 p. 663). On arrival in the intestine they burrow into Lieberkiihn's 

 follicles, and begin to lay their eggs. 



Pathogenicity. — ^The parasite is generally believed to cause a 

 catarrh of the small intestine, though many believe it to be non- 

 pathogenic. 



Family 4. Gnathostomid^. 



Nematoda, with two large lips and the whole or only the anterior 

 part of the body covered with minute ramified spines. They live 

 often in the tumours in the gut wall of vertebrates, especially 

 mammals. 



Two genera: Gnathostoma Owen, 1836, and Tanquct. 



