A degree of vascular turgescence visible to the naked eye is nearly always present in the mucous and submucous tissues which have been the seat of catarrh. It is usually found in the lower part of the ileum, the cæcum, sigmoid flexure, and other parts of the colon. The redness is diffused over a surface of several feet in length or is circumscribed in patches of varying size. When vessels of small size are distended with blood, red branching lines are seen (arborescent or ramiform injection) which have their starting-point in the insertion of the mesentery. When the capillary system is engorged a fine interlacing network can be discovered, which gives to the membrane a more uniform red color. Parallel lines or bands of redness extend in a transverse direction across the axis of the canal corresponding to the folds of mucous membrane in the small and large intestine.
The shades of color depend upon the intensity and duration of the congestion. In acute mild forms the color is light red; in more intense grades the membrane is more vivid or purplish. Brown and slate-colored tints show a passage into the chronic stage. A black hue occurs in gangrenous inflammation. Minute dots (speckled redness) are due to minute extravasations, and ecchymotic irregular patches are sometimes seen.
Bile-staining of the mucous surface is met with; this cannot be removed by washing. In metallic poisoning the redness is more vivid and the mucous membrane is eroded.18
18 For colored plates illustrating hyperæmia and inflammation of the intestines see Carswell, Path. Anat., London, 1838, plate ii. figs. 1 and 2. These are beautiful representations of (1) ramiform vascular injection passing into (2) capilliform injection, which becomes (3) uniformly red, or from its intensity (4) ecchymotic or hemorrhagic. See also Annesley, Morbid Anatomy, London, 1828, plates x. (Fig. 2), xiii., xxii., xxiv., and xxv. Many of these are illustrations of peritonitis as a complication of enteritis. See also Kupferlafelnzer, Lesser, Ueber die entzundung und Verschwarung der Schleimhaut des Verdauungskals, Berlin, 1830, tab. iv. fr. 3; also J. Hope, Illustrations of Morbid Anatomy, London, 1834, figs. 116, 118, 124, and 125. These plates are wonderful in their truthfulness and execution.
(b) Acute oedema and increase in the cell-elements in the inflamed parts give rise to swelling and to softening, so that the mucous membrane seems to be easily scraped off. This is not always the case, as no loss of firmness of the reddened tissue is often found. In the small intestine the villi, which in health are not seen, become enlarged, giving a "plush-like" or velvety appearance to the mucous membrane; they are sometimes club-shaped from epithelial accumulations on their free extremities.
(c) When the small intestine is examined the solitary glands, which in the normal state are barely visible, are so enlarged that they appear as rounded prominences. They are described as looking like grains of mustard-seed on a red ground, and are the size of pinheads. When they are distinctly seen it may be concluded that they are enlarged. In children the glands are enlarged when there has been slight or no diarrhoea.
Peyer's patches are also tumefied, and are more distinct from being elevated above the surface, but they have not in intestinal catarrh as great a relative enlargement when compared with the solitary glands as in typhoid fever. The interfollicular substance of the patch may hypertrophy without any increase in the size of the follicles; a reticulated appearance is then given to the gland. The color of the swollen follicles in recent inflammation is translucent from oedema; later they are gray and opaque. These changes are more marked at the lower end of the ileum, because the isolated follicles and Peyer's patches are more numerous there.
(d) Catarrhal ulcers—erosions—are produced by the loss of epithelium or from a process of vesicle-forming and rupture, as in stomatitis. They may enlarge, undermine, and coalesce, thus reaching quite a large size. They may deepen and perforate the wall of the bowel, causing peritonitis, or they may heal, forming cicatrices which in contracting may narrow the canal.
Small follicular ulcers are found on the mucous surface. They result from the breaking down of the exposed wall of the closed follicle from over-distension. The ulcer is either on the apex of the dome of an isolated follicle or is within the area of a Peyer's patch. Sometimes several ulcers may be seen on the surface of the swollen patch.19 The ulcerative process is sometimes very rapid. In the case of a child aged eight years, with no previous intestinal disease, who died in the Children's Hospital, Washington, in June, 1882, after a two days' illness with watery discharges and rapid prostration, the solitary glands throughout the ileum were many of them enlarged. As many as a dozen small ulcers were seen at the apices of the enlarged follicles.
19 See photograph facing page 302 of Med. and Surg. History of the War.