930 THE ORGANS OF DIGESTION. 



the rectum commence in a plexus of vessels which surrounds the lower extremity of 

 the intestinal canal. In the vessels forming this plexus are small saccular dilata- 

 tions just within the margin of the anus; from it about six vessels of considerable 

 size are given off. These ascend between the muscular and mucous coats for about 

 five inches, running parallel to each other ; they then pierce the muscular coat, 

 and, by their union, form a single trunk, the superior hemorrhoidal vein. This 

 arrangement is termed the hemorrhoidal plexus ; it communicates with the 

 tributaries of the middle and inferior hemorrhoidal veins at its commencement, and 

 thus a communication is established between the systemic and portal circulations. 

 The nerves are derived from the plexuses of the sympathetic nerve around the 

 branches of the superior and inferior mesenteric arteries that are distributed to the 

 large intestine. They are distributed in a similar way to those in the small intes- 

 tine. The lymphatic vessels of the large intestine are found in the submucosa, 

 where they form a wide-meshed network, and also, more deeply seated, beneath the 

 simple follicles. Those from the colon open into the mesenteric glands ; those from 

 the sigmoid flexure into the lumbar glands ; those from the rectum enter the glands 

 which are situated in the hollow of the sacrum ; and those around the anus open 

 into the glands in the groin. 



Surface Form. The coils of the small intestine occupy the front of the abdomen below the 

 transverse colon, and are covered more or less completely by the great omentum. For the most 

 part the coils of the jejunum occupy the left side of the abdominal cavity i. e. the left lumbar 

 and inguinal regions and the left half of the umbilical region whilst the coils of the ileum are 

 situated to the right in the right lumbar and inguinal regions, in the right half of the umbilical 

 region, and also the hypogastric. The caecum is situated in the right inguinal region. Its posi- 

 tion varies slightly, but the mid-point of a line drawn from the anterior superior spinous process 

 of the ilium to the symphysis pubis will about mark the middle 'f its lower border. It is com- 

 paratively superficial From it the ascending colon passes upward through the right lumbar 

 and hypochondriac regions, and becomes more deeply situated as it ascends to the hepatic flexure, 

 which is deeply placed under cover of the liver. The transverse coion crosses the belly trans- 

 versely on the confines of the umbilical and epigastric regions, its lower border being on a level 

 slightly above the umbilicus, its upper border just below the greater curvature of the stomach. 

 The splenic flexure of the colon is situated behind the stomach in the left hypochondritim, and 

 is on a higher level than the hepatic flexure. The descending colon is deeply seated, passing 

 down through the left hypochondriac and lumbar regions to the sigmoid flexure, which is situ- 

 ated in the left inguinal region, and which can be felt in thin persons, with relaxed abdominal 

 walls, rolling under the fingers when empty, and when distended forming a distinct tumor. The 

 position of the base of the vermiform appendix is indicated by a point two inches Ironi the 

 anterior superior spinous process of the ilium, in a line dravyn from this process to the umbilicus. 

 This is known as McBurneys spot. Another mode of defining the position of the base of the 

 appendix is to draw a, line between the anterior superior spines of the ilia and marking the 

 point where this line intersects the right semilunar line. 



Upon introducing the finger into the rectuin, the membranous portion of the urethra can 

 be felt, if an instrument has been introduced into the bladder, exactly in the middle line; 

 behind this the prostate gland can be recognized by its shape and hardness and any enlargement 

 detected ; behind the prostate the fluctuating wall of the bladder when full can le felt, and if 

 thought desirable it can be tapped in this situation ; on either side and behind the prostate the 

 vesiculae seminales can be readily felt, especially if enlarged by tuberculous disease. Behind, 

 the coccyx is to be felt, and on the mucous membrane one or two of Houston's folds. The 

 ischio-reetal fossae can be explored on either side, with a view to ascertaining the presence of 

 deep-seated collections of pus. Finally, it will be noted that the finger is firmly gripped by the 

 sphincter for about an inch up the bowel. By gradual dilatation of the sphincter, the whole 

 hand can be introduced into the rectum so as to reach the descending colon. This method of 

 exploration is rarely, however, required for diagnostic purposes. 



Surgical Anatomy. The small intestines are much exposed to injury, but, in consequence 

 of their elasticity and the ease with which one fold glides over another, they are not so frequently 

 ruptured as would otherwise be the case. Any part of the small intestine may be ruptured, but 

 probably the most common situation is the transverse duodenum, on account of its being more 

 fixed than other portions of the bowel, and because it is situated in front of the bodies of the 

 vertebrae, so that if this portion of the intestine is struck by a sharp blow, as from the kick of 

 a horse, it is unable to glide out of the way, but is compressed against the bone and so lacerated. 

 Wounds of the intestine sometimes occur. If the wound is a small puncture, under, it is said, 

 three lines in length, no extravasation of the contents of the bowel takes place. The mucous 

 membrane becomes everted and plugs the little opening. The bowels, therefore, may be safely 

 punctured with a fine capillary trocar, in cases of excessive distension of the intestine with gas, 

 without fear of extravasation. A longitudinal wound gapes more than a transverse, owing to 



