414 MUCOUS MEMBRANES. 



ordinary dIaiThoea are due to a "serous" transudation into the 

 small intestine. The serum of the l^lood, with its albumen and 

 salts, has passed directly from the vessels of the villi to the sur- 

 face ; it has been forced so rapidly down the bowel by violent 

 peristaltic movements, that the absorption in the large intestine 

 has not been able to keep pace with it. Choleraic catarrh differs 

 from ordinary diarrhoea, partly by the absence of albumen from 

 the transuded fluid (in cholera this consists entirely of water and 

 sodium chloride, Schmidt) ; partly by the implication of the 

 whole tract from the cardia to the anus ; finally by the volume 

 of the transuded fluid, and the rapidity with which it accumu- 

 lates. This rapidity is occasionally so great, that the epithelium 

 of the small bowel, together with the epithelial lining of the 

 follicles of Lieberhiihn, is strijDped off and swept away in shreds 

 of variable size (rice-water evacuations). On one surface of 

 these shreds, we see the long epithelial casts of the villi project- 

 ing like the fingers of a glove ; the opposite surface exhibits the 

 shorter and more globular outlines of the crypts of Lieherkithn. 

 The intestinal mucous membrane is left as if "flayed," and is 

 exposed without protection to the hostile action of its contents ; 

 a circumstance which must not be foro-otten in endeavourino; to 

 account for the patches of superficial gangrene, which the bowel 

 usually exhibits in the second stage of cholera. 



The " h^emorrhagic " form of catarrh differs from the 

 " serous" flux in the fact that the blood itself, and not merely 

 some of its constituents, aj^pears on the surface of the mucous 

 membrane. It is usually extravasated at the most prominent 

 points ; in the stomach, on the little bridges of connective tissue 

 which surround the orifices of the glands ; in the small intestine, 

 at the tips of the villi, and especially of those villi which beset 

 thelDorders of the folds of Kerkring ; in the ileum and colon, the 

 parts surrounding the follicular glands are chosen ; in the colon 

 moreover, the plicoi sigmoidece. The process itself consists in 

 what is known as " diapedesis." The blood forces its way in 

 minute quantities through correspondingly minute rents in the 

 flexures of the capillary loops, first into the parenchymatous 

 <>onnective tissue, and then on to the free surface. Should the 

 bleeding be arrested, some of the extruded blood-corpuscles are 

 retained in the parenchyma, where they are converted into a 

 brown or black pigment. Accordingly i\\(i mucous membrane 



