494 ABDOMEN 



another pair of ligatures round the left part of the transverse colon near the 

 left colic flexure. 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. In one piece carefully divide the longitudinal 

 bands of muscle in the intervals between the sacculi of the wall, then pull on 

 the extremities 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 experiment 

 shows that it is the shortness of the longitudinal bands which causes the 

 puckered condition of the wall of the large gut. Open both the separated 

 portions and note that the mucous membrane is devoid both of plicae 

 circulares and villi. Hold the wall of the intestine to the light and note that 

 whilst solitary lymph nodules are present there are no aggregated lymph 

 nodules. 



Structure of the Vermiform Process. The serous coat is complete, 

 and the subjacent -external longitudinal layer of the muscular coat forms a 

 continuous and uniform covering, which at the base of the process becomes 

 divided into the three bands or taenise coli of the caecum. The internal 

 circular fibres of the muscular coat are likewise spread uniformly and con- 

 tinuously over this part of the intestine. The distinguishing and important 

 structural feature of the vermiform process is found in the submucous coat. 

 This coat is loaded with lymph tissue which is arranged in numerous nodular 

 masses, like solitary lymph nodules, placed so closely together that ad- 

 jacent nodules in many cases become confluent with each other. When 

 the process is cut across and examined under a low power of the microscope, 

 these lymph follicles, arranged in this manner, present a strong resem- 

 blance to what is seen in a cross-section through an aggregated lymph nodule. 



Intestinum Crassum (Large Intestine). Structure of Large 

 Intestine. Transverse and oblique ridges or folds, correspond- 

 ing to the constrictions which separate the sacculi, are every- 

 where apparent on the inner surface of the large intestine. 

 If the longitudinal bands of muscular fibres be removed or 

 divided at short intervals, and the intestine stretched, both 

 sacculi and constrictions disappear, and the wall of the in- 

 testine becomes uniform. The mucous membrane of the large 

 intestine is absolutely destitute of villi, but solitary lymph nodules 

 are present in considerable numbers. If the mucous surface 

 be examined with a lens, its surface will be seen to be 

 studded over with the round mouths of tubular glands, which 

 are embedded in the mucous membrane (crypts of Licberkuhn). 

 The same glands are present in the mucous membrane of 

 the small intestine, but they are not so large. 



Dissection. The coats of the large intestine must be dissected in the 

 same manner as in the case of the small intestine. 



Coats of the Large Intestine. In connection with the 

 serous coat, the student has already taken notice of the appen- 



