chap, xvii.] THE COLON. 317 



width of the non-peritoneal surface varies from four- 

 fifths of an inch to an inch in the empty state, and 

 may attain to two inches or more in the distended 

 condition (Braune). The part of the descending colon 

 usually opened is the highest portion of that bowel, so 

 that the finger can often be thrust into the transverse 

 colon, or the opening of that intestine can be seen. 

 In this, or in other circumstances, the large bowel may 

 be distinguished from the small by its.sacculi, its three 

 longitudinal muscular bands, and its appendices epi- 

 ploicse. As regards dimensions, the small intestine 

 may, especially in cases of obstruction, be much larger 

 than the so-called large intestine. When empty, the 

 diameter of the descending colon is about equal to that 

 of the jejunum, the measurement in the two cases 

 being about one and a half inches. The average dia- 

 meter of the ileum is one and a quarter inches, and 

 of the caecum and commencing colon two and a half 

 inches. 



Lumbar colotomy is often performed through a 

 vertical or oblique incision in the place of the one just 

 given. The operation does not materially differ from 

 that described, when it is performed on the right 

 side. 



Colectomy consists in resecting a portion of either 

 the ascending or descending colon that is the seat of a 

 carcinomatous or other stricture. It is most con- 

 veniently performed in the lumbar region, and then 

 involves the formation of an artificial anus that will 

 probably be permanent. Colectomy, may, however, be 

 carried out through an incision in the middle line ; in 

 such a case the ends of the divided bowel are united, 

 and the abdominal wound closed.* Lumbar colectomy 

 may be performed through any one of the incisions 

 practised in colotomy. 



* See " Resection of Portions of Intestine," by the author. 

 Trans. Royal Med.-Chir. Soc., 1882. 



