6/2 



NEMA THELMINTHES 



5. Immature forms have been found again and again in blood-filled spaces 

 beneath the intestinal mucosa by Bilharz, Griesinger, Sonsino, Grassi, and 

 many other competent investigators. 



6. A number of other worms which inhabit the intestinal cavity at maturity, 

 such as CEsophagostomum, Sclerostomum, Ascaris, Gnathostoma, etc., in an 

 earlier developmental stage are usually found either free or encysted beneath 

 the intestinal mucosa. 



He also considers that when the larvae are taken in by way of the mouth 

 they probably pierce through the walls of the oesophagus like the larvae of 

 Hypoderma hovis (see Chapter XXXIII.), and reach their intestinal habitat by 

 way of the vessels in exactly the same way as those which penetrate the hair 

 follicle. 



Fiilleborn and von Schilling-Torgau have re-investigated the 

 subject by tracheotomizing dogs and inserting a cannula in such a 

 way that the larvae could not pass from the lungs to the oesophagus, 

 but only to the exterior. The dogs were then infected with 

 Ancylostoma caninum (Ercolani, 1859), ^-^^ after some time the 

 secretion from the cannula in the trachea swarmed with larvae. In 

 other dogs the oesophagus, not the trachea, was cut across and its 

 ends separately stitched to the skin, and after a time the secretion 

 from the upper cut end contained larvae. In both sets of experi- 

 ments the dogs became infected intestinally with only a very small 

 number of parasites. 



It is thus seen that Sambon's hypothesis is theoretically correct, 

 but Looss's route is the one by which the vast majority of the larvfe 

 enter the body. 



Pathogenicity. — It causes ankylostomiasis in man. 



Subfamily Bunostomin^ Looss, 1911. 



AncylostomidcB with small mouth capsule, with aperture nar- 

 rowed anteriorly by plates with cutting edges springing from the 

 sides, and more or less covering the ventral half of the aperture. 

 At the base of the cone which carries the opening of the dorsal 

 oesophageal gland there is on each side one tooth-like plate with 

 smooth edges. Coils of the genital tubes very numerous and close. 

 Externo-dorsal ray thin, more especially at the root. Spicule of 

 the male barbed at the end. 



Type Genus. — Necator Stiles, 1903. 



There are seven genera in the subfamily — viz., Bimostomum 

 Railliet, 1902 ; Necator Stiles, igo2;Brachy clonus Railliet and Henry, 

 1910 ; Gaigeria Railliet and Henry, 1910 ; Eumonodontus Molin emend. 

 Railliet and Henry; Bathmostomum Railliet and Henry, 1909; 

 and Grammocephalus Railliet and Henry, 1910; but only Necator 

 Stiles, 1903, concerns us. 



Necator Stiles, 1903. 

 Bunostominge closely resembling Ancylostoma, but distinguished 

 thereform by the small mouth capsule, which is armed only by 

 semilunar plates. The head is strongly bent dorsally. In the male 



