Laboulbène28 describes the gastro-intestinal false membrane as thin, soft, and granular, of a more or less yellow color, slightly adherent to the mucous membrane, and when stripped off forming a yellow pultaceous mass. He says it is first deposited in small, irregular, sparsely-scattered patches, located on the summits of the intestinal folds; afterward these patches increase, and cover the folds entirely and almost the whole calibre of the intestinal canal. The mucous membrane, he remarks, beneath the deposit is greatly inflamed.
28 Op. cit., p. 105.
Powell believes that at times the deposit extends as high as the duodenum, his opinion being solely based upon the clinical features of the disease. In the first of his cases the membrane was found in perfect tubes, some of them full half a yard in length, and certainly sufficient in quantity, he says, to have lined the whole intestinal canal.
In examining the membranes it is always best to float them from the fecal or other foreign material by passing the discharges in a clean vessel containing water. Their physical characters can then be readily studied. They are best preserved in a 10 per cent. solution of alcohol. The exudate consists usually of a single lamina, but at various points in certain cases several superposed laminæ may be observed, enclosing between them particles of undigested food of various kinds. In most cases the superficial layers are more opaque, drier, less elastic, and friable than the deeper.
The configuration of the exudate varies greatly. The more common variety is that occurring in loose, transparent, jelly-like masses, like the white of an egg or glue, tinged often with various hues of yellow. In three of my cases I noticed also the frequent occurrence of a thin, serous, yellow discharge. In some cases the discharge resembles pieces of macaroni, tallow, or wax; in others it assumes a shreddy or ribbon-like form; and in a still rarer class it is tubular, being an exact reprint of the surfaces from which detached. These tubular pieces are, however, more or less torn and broken into smaller fragments of an inch or two in length when discharged.
Its thickness also varies: sometimes it does not exceed that of the thinnest film, and at others it is a quarter of an inch or more.
Its consistence ranges from that degree of loose aggregation that permits elongation into stringy, breaking masses when fished up from the water in which it floats, to a firmness and tenacity that will enable it to be handled without fear of breakage.
The color differs in different cases. It is usually yellowish-white, but this is often modified by tints dependent upon admixture with extraneous matters from the intestinal canal—biliary coloring, blood from the rupture of the vessels beneath the exudate, or with blood and pus. It exhales a feculent odor.
The surfaces of the membranes are ordinarily smooth and uniform, but sometimes reticulated. Certain observers have described the outer surface of the tubular exudate as uniformly smooth, and the inner as broken and flaky at some points, at others ragged and flocculent, and in many places thrown into shallow folds, lying in some situations across, but chiefly along, the axis of the gut.
The microscopic characters of the exudate are pretty uniform. Wilks and Clark29 describe the surface of the tubes, examined with a linear magnifying power of forty diameters, as exhibiting the appearance of a gelatinous membraniform matrix traversed by a coarse network of opaque yellow lines, studded at their points of intersection by similarly colored rounded masses. From the larger network proceeds a smaller secondary network, and in the recesses of this were found, at close and regular intervals, well-defined round or oval openings, with elevated margins, resembling in size and appearance the mouths of the follicles of the great gut. With higher powers the exudate was found in many cases to consist of a structureless basement membrane, which in certain points showed a fibrous appearance, owing doubtless to the presence of filaments of mucin. Numerous irregular granular cells, as well as granules from the breaking up of these cells, thickly studded the surface of the membrane. In the specimens of Wilks and Clark the surface, besides being marked by the opaque yellow lines and dots, presented various foreign matters, such as bile-pigment, earthy and fatty granules, portions of husks of seed, gritty tissues of a pear, a peculiar form of elastic tissue, stellate vegetable hairs, and a mucedinous fungus. Clark, in describing the fibres found between the layers of the exudates, says that they exhibited a very distinct and regular transverse striation, approaching in character that found in the ligamentum nuchæ of the giraffe. Quekett and Brooke have met with the same fibres in the feces. The transverse division depends probably upon beginning decay. The division is sometimes so distinct and complete as to lead, according to Beale,30 to their confounding with confervoid growths. Farre31 actually describes the formation as of a confervoid character.