The congenital malformations belonging to this section, are the anomalies which we have described above, when speaking of the length of the intestine, and the true diverticulum.

The acquired malformations, as distinguished from the former, have reference to the calibre of the intestine, and are either dilatations or contractions.

The former occur either as uniform dilatations of the tube, or a lateral extension.

Uniform dilatation is the result of atony, or paralysis, consequent upon concussion, habitual repletion, peritonitis, rheumatism, typhus, dysentery, cholera, overstimulation by injections and purgatives, and the like; or it is the immediate consequence of disease in the nervous centres; or the dilatations may be developed as dilatations of an active character, i. e. with hypertrophy of the muscular coat above a constriction. In accordance with their etiological relations, they occur chiefly in the colon.

The lateral dilatation of the intestine occurs in a form resembling a diverticulum, constituting the false, in contradistinction to the true diverticulum; it is a hernia of the intestinal mucous membrane, resulting from the separation of the fibres of the muscular coat. It differs in every one of its characters from the true diverticulum:

1st. False diverticula consist solely of mucous membrane and peritoneum;

2d. They occur at the duodenum, in the entire course of the small and large intestines;

3d. They are found in considerable numbers;

4th. They occur from the size of a pea to that of a walnut, in the shape of round, baggy pouches of the mucous membrane;

5th. They form, more especially in the colon, nipple-shaped appendages, which occasionally are grouped together in bunches; when occurring in the small intestine, they are commonly developed on its concave side, and are therefore placed between the layers of the peritoneum; when in the colon, the faeces are retained by them, and dry up into stony concretions.

Contraction of the calibre of the intestine at a small portion, or in a greater extent, is the effect of the pressure or traction exerted by large morbid growths, by hypertrophied contiguous organs, the impregnated uterus, uterine fibroid tumors, dropsy or cancerous degeneration of the ovary, etc.; it is brought on by incarceration or traction of the intestine in external and internal herniae, by invagination, by adhesion of the intestine, accompanied by angular inflection at the point of adhesion; by compression of a large portion of intestine into a small space, in consequence of a firm adhesions between the coats and the peritoneum; it is produced by disease of the tissues, and more especially by cancer (cancerous stricture), by cicatrization of tubercular ulcers, by the healing of loss of substance in dysentery, by catarrhal suppuration, by the scar following a gangrenous slough, or by simple hypertrophy. The passage of the intestine is moreover interfered with or entirely obstructed, by tumors which project into the intestinal cavity, and it is variously affected by foreign bodies.

We have lastly to remark, that we find various states of contraction and vacuity of the intestine coexistent with its blind termination, with an artificial anus, or with stricture.

In a different point of view we must here cite the anomalies which occur in the dimensions of the intestinal parietes: they appear in the shape of augmentation or diminution, i. e. thickening or thinning. Thickening is found to accompany or result from textural diseases, under which head this form will be considered; but it also presents itself as simple hypertrophy.

This either affects the mucous membrane and the muscular coat separately, or both simultaneously, together with the intervening cellular tissue. In the first and last cases it is the result of a repeated and habitual state of irritation of the intestinal mucous membrane, which, in accordance with a uniform law, after a certain duration gives rise to hypertrophy of the muscular coat, and an increase in the density and quantity of the intervening cellular layer. The hypertrophy of the mucous membrane is presented to us in a very characteristic shape in polypus of the intestine; this growth is peculiar to the colon, and chiefly to its terminal portion, being often remarkable for its length, its frequent repetition, and the massive cauliflower-like development of its free extremity. When hypertrophy exclusively or mainly affects the muscular coat, it generally results from excessive innervation accompanying habitual spasm of the intestine, or from extreme excitement of its muscular activity induced by repeated or continual repletion, as we see following a stricture.

Excessive thinning of the intestinal mucous membrane, presenting an appearance which resembles that of serous membranes, occurs chiefly in the colon after the protracted serous diarrhoeas which accompany consumptive diseases; the tissues are there found in an anaemic and pallid condition, without exhibiting any conspicuous anomaly in consistency.

Atrophy of the muscular and mucous coats of the intestine is often seen in connection with tabes universalis, though rarely as it appears, dependent upon idiopathic torpor of the abdominal ganglia; it is found coexistent with a wasting of the mesenteric glands in hypochondriac and melancholic affections, or as a signal of certain acute processes, as for instance, of typhus, or as a consequence of slow poisoning by lead. The thinning which, coupled with relaxation and friability of the intestinal membranes, occasionally exists simultaneously with an accumulation of fat in the mesenteries and omentum, is still more remarkable. The excessive production of fecal matter (copropoesis excedens) which frequently accompanies these two conditions, is important in reference to their pathogeny.

The follicular apparatus frequently becomes atrophied at an advanced age, but it may be similarly affected in consequence of acute diseases, such as ileo-typhus. Berres has demonstrated senile atrophy in the intestinal villi.