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i. The oesophagostome larvae * as stated by Weinberg, reach the 
bowel by way of the blood. The larvae rupture a small blood vessel 
and become encysted in the submucosa, in the internal or external 
muscular coats of the bowel or in the subperitoneal space. In no case 
has a cyst been found above the level of the muscularis mucosae. The 
favourite sites for the development of the cysts appear to be in the 
submucosa and external muscular coat with invasion of the sub- 
peritoneal space. Cysts developing primarily in the internal muscular 
layer are not uncommon. The subperitoneal space appears to be a 
favourite site for the cysts of the ileum, but in the caecum and colon 
it is extremely rare to find a subperitoneal cyst. Nearly all the cysts 
have developed in the outer fibres of the external muscular coat and 
have immediately extended to the looser tissues of the subperitoneal 
space. In no case has a cyst been found to contain more than one 
worm. 
2. The worm can moult and become an immature oesophagostome 
and leave its cyst cavity. Weinberg has found them in the lumen of 
the intestines. An empty cyst can become cicatrized or calcified. 
Acute inflammation of a cyst does not affect the larva. 
Necrosis of one cyst can extend to another one lying in the 
immediate vicinity. The amount of infiltration around a cyst depends 
to a certain extent on the amount of irritation produced by the worm. 
Weinberg has shown that the cesophagostome can produce haematoxic 
substances analagous to those secreted by the sclerostome of the horse, 
and it is probable that this affords an explanation of the number of 
eosinophiles observed around some cysts and not around others, 
although they may be lying close at hand. The infiltration can be 
induced by bacilli entering the cyst by way of the blood stream, or by 
ulceration of the distended mucous membrane. 
The haemorrhagic contents of the cysts and the degeneration of 
the blood cells cause the formation of iron pigment, which can be 
taken up by large leucocytes and conveyed to the subperitoneum. 
Iron pigment has been found in large quantities in the spleen and, 
to a less extent, in the liver and mesenteric glands. 
* The larvae obtain nourishment from their host. Many erythrocytes have been found 
in the lumen of the intestine of a worm. Pus cells and bacilli are frequently found if 
the contents of the cyst are septic. 
