Emotional influence, as sudden fright or grief, will produce sudden diarrhoea. Lesions of nerve-centres—corona radiata, optic thalamus, or corpus callosum—induce hyperæmia, softening, and ulceration of the mucous membrane of the small intestine.15
15 Rosenthal, "Diseases of the Nervous System," Wood's Library, New York, 1879, vol. ii. p. 266.
Minute organisms (bacteria) are thought by some observers to be the cause of diarrhoea, especially of a zymotic form, which prevails in the summer months. In accordance with this theory, the dejecta from infected persons are the vehicle of the contagious poison which by air- and water-contamination infects others.16
16 Wm. Johnston, Lancet, London, 1878, vol. ii. p. 397; also, Brit. Med. Journ., London, 1879, p. 81; also, G. E. Paget, "On the Etiology of Zymotic Diarrhoea," Brit. Med. Journ., Nov. 19, 1881, p. 819.
PATHOLOGICAL ANATOMY.—A description of the morbid anatomy of acute intestinal catarrh includes the changes which are observed (1) in the exterior appearances of the intestines, (2) in their contents, and (3) in the condition of their mucous lining.
1. The external appearances of the intestines depend upon the degree of distension of the tube, the character of the contents, and the presence or absence of inflammation of the serous coat. Great distension of the colon, of the cæcum, and of the small intestines is met with in acute intestinal catarrh of some duration, and is due to relaxation of the muscular coat. The colon usually presents the greatest distension. The calibre of the tube may be lessened by strong contraction of the muscular layer in acute intestinal inflammation of great intensity with early and fatal termination. The color of the exterior varies with the tension of the wall, the color of the contents, and the amount of vascular injection. If the bowel is much distended with gas, the color is pale; the mingling of bile with the feces causes a yellowish or brownish color; if blood is in the tube a dull red hue is given to the walls. If the intestine is congested or inflamed, the vessels are outlined distinctly and can be seen in different layers. The areas of external redness generally correspond to internal hyperæmic patches. The serous membrane shows arborescent congestion at the mesenteric attachment or is inflamed from perforation; the signs of peritonitis are most marked in the neighborhood of the irregularly-shaped, round, oval, or pin-point openings in the gut. The abdominal cavity may contain fecal matter, food, medicines, or worms which have passed through the perforation.
2. The intestinal contents, instead of being homogeneous, of pale-yellow color, and pea-soup-like appearance in the small intestine, brown and more condensed in the lower part of the large intestine, may present various changes. The fluid is usually increased in quantity, and is thinner than normal in the colon: the color is greenish from the bile, very pale from the closure of the bile-duct, red or black from blood. The odor is absent from excess of serum, or very offensive from decomposition due sometimes to the closure of the common bile-duct and the want of bile. Shreds or masses of mucus may float in the liquid. Undissolved pills or drugs, as bismuth, accumulated seeds, skins of fruits or vegetables, parasites, or foreign bodies are seen. Epithelial cells, the débris of digestion, micrococci, and bacteria are visible under the microscope.
3. Inflammation involving the mucous membrane of the whole intestinal canal is rarely or never met with. The nearest approach to generalized catarrh of the bowel is found in eruptive fevers, especially measles. Inflammation extending throughout the whole length of either the small or large intestine alone, and affecting all parts equally, is also rare. The ileum is the part of the small intestine most frequently the seat of disease, but the ileum is rarely affected alone. Inflammation is more frequently limited to the colon than to the small intestine. The most common form of intestinal inflammation is ileo-colitis, where the lower part of the ileum and a part of the colon, sometimes of considerable extent, are inflamed. The duodenum is sometimes the seat of a local inflammation, but this rarely happens except in the case of external burns; duodenitis is most frequently an extension of catarrh from the stomach, but the pathological anatomy of the duodenum presents some peculiarities which will be described hereafter.
(a) Hyperæmia of the intestinal mucous membrane may exist without inflammation. The engorgement of the veins by mechanical retardation in disease of the liver, heart, or lungs does not constitute catarrh, although it is sooner or later followed by catarrhal processes, usually of a chronic nature. Gravitation of blood to the most dependent parts in cases of long illness distends the vessels, and post-mortem hypostasis leads to the passage of serum and coloring matter into the meshes of the mucous and submucous tissue. In fatal cases of acute diarrhoea sometimes no lesion has been observed. The hyperæmic membrane pales after death, as does the skin in scarlatina and erysipelas.17 The presence or absence of hyperæmia is therefore no positive proof of the previous existence or non-existence of inflammation. To constitute inflammation there must be other changes besides hyperæmia, as oedema, softening, and infiltration with cell-elements.
17 It is difficult to recognize post-mortem hyperæmia in the mucous membrane of the mouth or throat where intense inflammation has been seen in life.