STRONGYLOIDES STERCORALIS 381 



species, and described them as A. intestinalis. Both forms were then regarded 

 as the cause of Cochin China diarrhoea until, in 1882, Leuckart was able to 

 demonstrate that the two forms are only two succeeding generations of the same 

 species, of which the one (A. intestinalis] lives parasitically in the intestine, 

 whereas its young (A. stercoralis] attain the open, where they come to maturity 

 and propagate. The young of these again live parasitically. There thus exists 

 the same heterogony as was discovered by Leuckart in Angiostomum nigro- 

 venosum of frogs, which heterogony, indeed, according to v. Linstow, appertains 

 to the entire family of the Angiostotnidce. 



(1) The parasitic generation (strongyloid or filariform ?) is quite 

 colourless and cannot be seen in situ even with a lens. To detect 

 them it is necessary to scrape the mucosa of the jejunum and examine 

 the scrapings microscopically. It measures 2*2 mm. in length, and 

 34 fjb to 70 fjb in breadth ; the cuticle is finely transversely striated ; 

 the mouth is surrounded by four lips ; the oesophagus is almost cyl- 

 indrical and a third the length of the entire body. The anus opens 

 shortly in front of the pointed posterior extremity ; the vulva is 

 situated at junction of middle and posterior thirds of the body; the 

 uterus has no special ovejector; the eggs measure 50 //, to 58 p in 

 length, and 30 p to 34 //, in breadth, and lie in a chain one behind 

 the other (fig. 270). As in the case of Angiostotnum nigrovenosum, 

 Leuckart considers this stage to be hermaphroditic, the testes 

 degenerating after having functioned ; other authors (Rovelli) regard 

 it as a female reproducing by parthenogenesis. 



(2) The free-living generation ( $ and ) has a smooth body, 

 cylindrical, somewhat more slender at the anterior extremity and 

 pointed at the tail end. The mouth has four indistinct lips ; the 

 oesophagus is short with a double (rhabditis-like) bulb ; there is a 

 Y-shaped valve in the posterior bulb ; the anus opens in front of the 

 tail end. The males measure 0*7 mm. in length, 0*035 mm. i n breadth. 

 Their posterior end is rolled up ; the two brown spicules are small 

 (38 fju) and much curved. There is also a gubernaculum. The 

 females measure i mm. in length or a little over ; 0*05 mm. in breadth. 

 The tail end is straight and pointed ; the vulva lies somewhat behind 

 the middle of the body. The yellowish, thin-shelled ova measure 

 70 //, in length and 45 //, in breadth. 



As Askanazy has shown, the parasitic form bores deeply into the 

 mucous membrane of the intestine, and frequently into the epithelium 

 of Lieberkuhn's glands, both for nourishment and oviposition. The 

 eggs then develop in the intestinal wall. The eggs which are found in 

 scrapings from the mucosa occur, at least in the case of Strongyloides 

 of the sheep, in chains enclosed in a thin tube or sheath, the origin 

 of which is doubtful ; possibly it is the uterus. The eggs them- 

 selves are only rarely found in stools, e.g., after a strong purge. The 

 larvae, which are hatched out, and measure 0-2 to 0*25 mm. long by 



