401 



STOMACH AND INTESTINE. 



co-existence of a diverticulum with the nor- 

 mal pouch of this part. 



The diverticula of the intestinal canal seem 

 to be of two kinds, which differ, not only in 

 the frequency of their occurrence, but also 

 in their situation, form, structure, and (in all 

 probability) in their nature or import. 



The least common variety form pouches of 

 variable length, width, and shape ; which 

 may spring from almost any part of the canal, 

 but are usually connected with the small intes- 

 tine. Their structure varies ; but, as con- 

 trasted with the bowel itself, they usually 

 exhibit more or less deficiency of the mus- 

 cular coat.* 



The true diver ficul um differs materially from 

 these. It usually forms a short tube of in- 

 testine, which leaves the ileum at from 1 to 2 

 feet above its termination ; by what is either 

 a right angle, or is such as gives it an incli- 

 nation towards the lower part of the bowel. 

 Its width generally approaches that of the 

 ileum, with which its cavity is continuous, 

 by an aperture that is sometimes valvular. 

 It possesses the ordinary muscular and mu- 

 cous coats. The former exhibits its usual 

 transverse and longitudinal layers. The latter 

 also presents its ordinary structure : being 

 occupied by villi, tubes, and follicles ; and 

 sometimes, by valvula3 conniventes of remark- 

 able distinctness for this region of the bowel. 

 Its length is generally about three or four 

 inches. Its shape is more or less cylindrical, 

 oftener contracting than expanding towards 

 its termination. It commonly sustains vessels, 

 and is attached by a kind of mesentery. Oc- 

 casionally it exhibits, in addition to these 

 vessels, a cellular cord that evidently contains 

 the degenerated relics of some large artery. 

 And finally, it sometimes extends upwards 

 towards the umbilicus ; and, in rare instances, 

 opens here. From all these circumstances 

 there can be little doubt of its true import 

 being that assigned to it by Meckel ; namely, 

 that itis a highly developed and persistent por- 

 tion of the duct of the umbilical vesicle. 



(3.) The third or remaining group of mat- 

 formations includes most of the congenital 

 displacements of the digestive canal. These, 

 as already mentioned, may be ascribed to two 

 very different causes. The transposition or 

 displacement of the tube within the abdomen, 

 whether total or partial, is a fact for which 

 the history of its development affords no ex- 

 planation or probable secondary cause.-j- 

 While the situation of any part of the canal 



* Hence some anatomists regard these pouches 

 as constituting a kind of hernia of the mucous 

 membrane. But unless this view imply that they 

 are, at least in part, of mechanical origin, it can only 

 amount to a circuitous statement (and often an 

 exaggerated one) of the above fact. It is however 

 probable, that some of these diverticula really are 

 the results of accident. 



f In rare instances, the stomach or colon take a 

 vertical position, which, to some extent, suggest an 

 arrest of their development. But little stress can 

 be laid upon such a conjecture, unless it be con- 

 firmed by other appearances of the same kind in 

 these or neighbouring parts. 



externally to the cavity of the bell}', is, in 

 most instances, the mere result of a defi- 

 ciency of the abdominal parietes. 



The partial displacement of the canal gene- 

 rally affects the transverse colon, or some 

 other segment of the large intestine ; and, 

 more rarely, the stomach. Its total transpo- 

 sition inverts the position of all the abdominal 

 viscera with respect to the median line: so 

 that, for example, the pylorus, the ccecum, 

 and the ascending colon occupy the left side 

 of the belly ; while the cardia, the descending 

 colon, and its sigmoid flexure, are found on 

 the right, or opposite side. 



The congenital inguinal herniae form the 

 most familiar illustration of the second (or 

 extra-abdominal) class of displacements. And 

 when a similar arrest of development involves 

 the anterior wall of the belly generally, the 

 abnormal situation of the canal may assume 

 any grade, from that of a limited umbilical 

 hernia, to an external situation of almost all 

 the intestinal canal. While the deficiency of 

 the diaphragm may allow a variable extent of 

 the canal to occupy the cavity of the thorax. 

 From obvious reasons, it is the commence- 

 ment of the small intestine, which usually 

 experiences this displacement. The stomach, 

 above the hernia, is sometimes dilated. 



Morbid Conditions. Size. Alterations in 

 the size of the alimentary canal, though they 

 chiefly affect its calibre, are generally asso- 

 ciated with changes in its walls. 



Constriction. Narrowing or diminution of 

 calibre is sometimes general, hut is more fre- 

 quently limited to a part of the tube. Its 

 causes are various. 



1. It often results from a process of con- 

 traction, which specially engages the muscular 

 coat. Such contraction, generally passive, is 

 well exemplified in the narrow empty tube, 

 seen where the canal has for some time re- 

 ceived no contents. Thus in persons who 

 have died of starvation, the intestines are 

 sometimes reduced to a tube, with pale thick 

 walls, and a narrow calibre, like a tobacco- 

 pipe. While a more local change of the 

 same kind is often found in the empty seg- 

 ment of the intestine immediately below an 

 obstruction, or an artificial anus. During its 

 rigor mortis, the dead intestine often presents 

 similar appearances. These may, however, 

 be distinguished by their originating in a more 

 active contraction, by their exhibiting a more 

 marked, but less permanent character, and by 

 their involving a less extent of bowel. And 

 lastly, various irritants and astringents have 

 been found to excite the muscular coat to 

 contractions, which can more or less imitate 

 the diminution of calibre producible by the 

 preceding causes. 



2. Narrowing may also result from the con- 

 traction of other intestinal tissues, besides the 

 muscular coat. The constriction produced 

 by the immediate or local action of the corro- 

 sive poisons on the alimentary canal, may be 

 partially ascribed to their direct chemical in- 

 fluence on the various textures with which 

 they come into contact. Such poisons, for 



