ABDOMINAL CAVITY 337 



colon, the dissector should again examine the longitudinal 

 muscle fibres of the walls of the large intestine. They are 

 arranged in the form of three longitudinal bands (tcenice coli). 

 The bands converge together on the medial and posterior 

 aspect of the caecum and fuse into a continuous layer on the 

 vermiform process. At the other end of the large gut they 

 unite again, on the wall of the rectum, first into two bands 

 and then into a continuous layer, but in the intervening parts 

 of the large intestine the bands are widely separated, one 

 running along the anterior border (tania libera\ one along 

 the posterior border (tcznia mesocolica\ whilst the third lies 

 along the medial borders of the ascending and descending 

 portions of the colon, and along the lower border of the 

 transverse colon (tcenia omentalis\ 



Dissection. Place two ligatures round the upper part of the 

 ascending colon, immediately below the right flexure of the 

 colon ; divide the intestine between the ligatures and remove 

 the caecum and ascending colon. Place two ligatures round 

 the transverse colon, to the left of the right flexure of the colon, 

 and another pair of ligatures round the left part of the transverse 

 colon, near the left flexure of the colon. Divide the transverse 

 colon between the ligatures at each end ; then cut the transverse 

 colon away from the remains of the transverse meso-colon and 

 its contents. Take the separated portions of the large intestine 

 to the sink, remove the ligatures and wash out the cavity of each 

 part with running water. 



When the washing is completed divide the separated portion 

 of the transverse colon into two equal parts. In the case of one 

 of the two parts, carefully divide the longitudinal bands of 

 muscle, in the intervals between the sacculi ; then pull upon the 

 extremities of the separated portion of the gut and note (i) 

 that the intestine lengthens, (2) that to a great extent the sacculi 

 disappears, and (3) that when the tension is removed the piece of 

 intestine does not return to its former length. This simple ex- 

 periment shows that it is the shortness of the longitudinal bands 

 which causes the puckered condition of the wall of the large gut. 



Now open the ascending colon, and the two parts of the 

 transverse colon, and note that the mucous membrane of the 

 large intestine is devoid both of plicae circulares and of villi. 

 Note, further, that in the ascending colon and that part of the 

 transverse colon in which the longitudinal bands of muscle were 

 not divided the mucous membrane is thrown into a number of 

 transverse and oblique folds and ridges some of which corre- 

 spond with the constrictions between the sacculi but others are 

 independent of those constrictions, whilst in that part of the 

 transverse colon in which the longitudinal muscle bands were 

 stretched, after the longitudinal bands of muscle were divided, 

 folds and ridges of the mucous membrane are practically absent. 

 Obviously, therefore, in ordinary circumstances the mucous 

 membrane of the large intestine is much more extensive than the 

 other layers of the wall of that part of the gut. Indeed if the 

 VOL. II 22 



