366 



STOMACH AND INTESTINE. 



position. The shape of this bend corresponds 

 so exactly to its name, that it is scarcely 

 necessary to bestow any further description 

 upon it. Its curve is chiefly in the vertical 

 plane ; though a slight lateral curvature is 

 almost always present, and is easily exag- 

 gerated into a much more distinct bend by 

 the mobility of this segment of the canal. 



The use of the sigmoid flexure seems to be 

 that of forming a receptacle for the faeces : 

 a receptacle of which the shape and arrange- 

 ment are such as to spare the rectum and its 

 sphincter from much of the pressure and 

 weight against which they would otherwise 

 constantly have to contend. When full, the 

 convexity of its lower bend often projects 

 below the iliac fossa, so as to descend into the 

 pelvis. Indeed, the whole of the colon is very 

 liable to displacement from the various po- 

 sitions just assigned to it: prolonged dis- 

 tention by its accumulated contents, or the 

 mechanical force exerted by the pressure of 

 stays externally, or of tumours internally 

 being all capable of altering its relations, and 

 even confusing its different parts* with each 

 other. 



The colon retains the sacculated shape as- 

 sumed by the cascum. Its size undergoes a 

 progressive though slight decrease, from its 

 commencement in the caecum to its termina- 

 tion in the rectum. Its peritoneal coverings 

 reach their minimum in the ascending and 

 descending portions ; where they only cover 

 about two-thirds of the moderately distended 

 bowel, and leave its posterior or attached third 

 quite unoccupied by this membrane, and con- 

 nected by loose areolar tissue to the subjacent 

 parts. Hence it is these portions of the bowel 

 which are selected in the operation for artificial 

 anus, -f- But, just as great distention can 

 always increase this uncovered portion, so, 

 vice versa, excessive contraction may reduce 

 it to a mere line, or may even develope a kind 

 of short meso-colon in connection with either 

 of these parts. The muscular strata which 

 cause its sacculated shape, also retain the 

 arrangement existing in the coecum. But on 

 the transverse colon, the internal longitudinal 

 band becomes inferior. And on the sigmoid 

 flexure, this and the posterior band generally 

 merge into a single one. The latter change 

 is accompanied by an indistinctness of the 

 transverse sacculi themselves. 



Throughout the whole of the large intestine, 

 the peritoneum is here and there developed 

 into peculiar, processes, called the appendices 

 cplploiccB (t?ri rXoov, omentum). These are 

 short pouches of the serous membrane, which 

 generally form flattened duplicatures or folds. 

 They are prolonged from the peritoneum cover- 

 ing the surface of the intestine itself; and are 

 therefore absent from that portion of the 

 rectum, or terminal segment of the large in- 

 testine, which does not receive any covering 



* See Abnormal Anatomy. 



f Other things being equal, the left or descend- 

 ing portion is preferred : on account of a larger 

 extent of the canal being thus left to be traversed 

 by the intestinal contents. 



of this membrane. Their number, size, and 

 arrangement, are liable to great variety. Some- 

 times they are so numerous, as to form a 

 single or double row along the free surface 

 of the bowel. In other instances they are 

 very few and imperfect. Their size is so 

 far related to the state of the bowel, that, 

 like most other processes of peritoneum, they 

 are enlarged by its contraction, and dimi- 

 nished by its distention. From their con- 

 tents, which consist of areolar and adipose 

 tissue, they would seem to be small reser- 

 voirs of fatty matter. Hence in cases of re- 

 markable obesity, their size is much increased. 

 Indeed they sometimes acquire a length of 

 one or two inches ; and have even been 

 known to encircle and strangulate the bowel. 



Movement of the large intestine. The exact 

 nature of the movement which is executed by 

 the muscular coat of the large intestine can 

 at most only be conjectured from some of its 

 attendant circumstances. Like that of the 

 preceding segment of the canal, though its 

 general mechanism is obvious, its details remain 

 unknown. 



As regards the investigation of the con- 

 tents of this intestine in its ordinary situation 

 during life, all that can be stated is, that, 

 even in health, they include a quantity of 

 gaseous matter ; which usually maps out the 

 ccecum, and more or less of the colon, with 

 tolerable distinctness, from the less resonant 

 convolutions of the small intestine. 



After death, the quality and quantity of these 

 contents are so much affected by the nature of 

 the previous food, the mode of dying, and a va- 

 riety of kindred causes, that scarcely any gene- 

 ral proposition can be laid down with respect to 

 them. But on the whole, we usually find, that 

 in addition to much gaseous fluid, the cascum 

 of the healthy subject is partially distended 

 by pultaceous or semi-fluid contents. While 

 the colon is occupied at various points of its 

 length by matter, the faecal character of which 

 is still more distinct, and the consistence of 

 which gradually increases as it approaches the 

 rectum. 



W here these rudimentary faeces are very im- 

 perfect, scanty, and interrupted, they only oc- 

 cupy some of the sacculi or cells of the bowel, 

 leaving its central or general calibre in an empty 

 state. But when better developed, they form 

 what is termed a " figured " mass. This con- 

 sists of a kind of central rod, that corresponds 

 to the general axis of the tube; and of processes 

 that come off from the sides of this axial por- 

 tion, and are contained in the rows of pouches 

 formed by the wall of the bowel. In short, 

 the solid and continuous faecal substance forms 

 a tolerably perfect cast of the bowel ; a cast 

 in which the sacculi of the colon are "figured " 

 as projections, themselves isolated by depres- 

 sions corresponding to the intersections of 

 its longitudinal and transverse bands. 



The characteristic shape thus possessed by 

 the solid contents of the colon, is often retained 

 by the faeces which have been forced through 

 the rectum in the natural process of defaeca- 

 tion. And although it is often absent, the con- 



