i686 HUMAN ANATOMY. 



(i^ in.) at the lower end of the sigmoid flexure. Its average capacity in infants 

 of six months is Y^ litre (i pint); in children two years old, 1.25 litres (2.5 pints); 

 and in adults, 4.5 litres (9 pints). 



It is normally palpable through most of its extent, the more deeply placed 

 hepatic and splenic flexures excepted, the former being beneath the liver, the latter 

 behind the cardiac end of the stomach. The ascending and descending portions are 

 usually overlapped in front by the more mobile small intestine, which, if not dis- 

 tended, can be displaced towards the median line. The thickened and sometimes 

 tender edge of a chronically congested or inflamed caecum can often be rolled under 

 the finger against the floor of the iliac fossa, and has been mistaken for the appendix. 



The colon is susceptible of great distention, and in cases of obstruction in the 

 sigmoid flexure or rectum it may occupy most of the abdomen, push up the dia- 

 phragm, displace the heart, and occasion dyspnoea and palpitation. 



Distention either from gas or fecal accumulation renders the colon visible, as 

 well as palpable, except at the flexures. In chronic obstruction in the rectum or 

 sigmoid its peristaltic movements may be seen through the thinned abdominal walls. 

 In the common ileo-caecal variety of intussusception the tumor can often be seen as 

 well as felt, and sometimes the progress of the intussusceptum along the colon can 

 be traced with the eye. 



Tumors of the colon or upper end of the sigmoid are often visible in thin pa- 

 tients, especially when they have contracted anterior parietal attachments. 



Distention of the colon gives rise to prominence and outward curving of the 

 flanks, as the patient lies supine, and to fulness below the costal arches and the 

 margin of the liver. The anterior surface of the belly — taking the umbilicus as a 

 centre — is relatively flat. In distention of the small intestine the swelling is most 

 marked in the latter region. 



Normally the colonic percussion-note is of somewhat lower pitch than that of 

 the small intestine, but of higher pitch than that of the stomach, the variation being 

 due to the difference in the size of these viscera and in the thickness of their walls. 

 In general gastro-intestinal distention the same variations are often observable. 



A large quantity of fluid faeces in the colon will give rise to percussion dulness 

 in the flanks, which may disappear when the patient is turned on his side. That 

 sign is therefore not conclusive evidence of the presence of free fluid in the peri- 

 toneal cavity, unless the condition of the colon is known. 



Rupture from distention — a rare occurrence — will usually be incomplete, the 

 mucous membrane remaining unbroken. 



Idiopathic dilatation of the colon has been seen in young children, chiefly among 

 those affected with rickets. 



Displacements. — The caecum and ascending colon or the sigmoid and descend- 

 ing colon may be found in inguinal or femoral herniae, may be at the median line of 

 the body, or may even lie in the iliac fossa of the opposite side. A misplaced, 

 moveable, or enlarged kidney may cause variation in the position of the colon. 

 " When the left kidney occupies the iliac fossa or is situated over the left sacro-iliac 

 synchondrosis there is generally no sigmoid flexure in the left iliac fossa ; but the 

 descending colon passes across the middle line, and the rectum commences on the 

 right side of the sacrum" (Morris). Paranephric tumors, by pressure on the colon, 

 have produced such marked symptoms of intestinal obstruction as to be mistaken 

 for intussusception (Ibid. ). 



The transverse colon, as the most movable of the three divisions of the colon 

 proper, is peculiarly liable to assume abnormal positions, usually as a result of 

 habitual constipation or secondary to obstruction lower in the gut. It can readily 

 be understood how the weight of fecal masses may in time exaggerate the normal 

 downward curve of the transverse colon, resting only on the easily displaced small 

 intestine, and carry it towards the pubes, which it sometimes reaches. The normal 

 level of the middle or lower portion of the transverse colon is at the upper umbilical 

 or the lower epigastric region, or on the line separating those two regions. The 

 position of the transverse colon in relation to the stomach varies greatlv within 

 normal limits. If the stomach is empty, it is behind the colon; if full or distended, 

 it will push the latter downward and overlap it from in front. 



