234 DR. p. CHALMERS MITCHELL ON THi: 



large series of irregular minor loops, nearly completing the 

 periphery of an oval expanse of mesentery. The recurrent 

 limb of the pendant loop also enters into the formation of 

 Meckel's tract, and the short, rounded caecum lies just where the 

 pendant loop bends round at its highest point to pass into the 

 hind-gut. 



The distal end of the ileum projects through into the cavity of 

 the hind-gut at an angle, the projection being much greater on 

 the ca^cal side. The cavity of the ciecum is, as is usual, a forward 

 continuation of the cavity of the hind-gut. There is no trans- 

 verse colon, the gut, at the highest point of the distal end 

 of the recurrent loop, bending round sharply to the rectum. 

 There is, in fact, practically no true colon, but the rectum is 

 considerably longer than the course that it has to traverse, and 

 is thrown into a number of minor loops. 



I have recently had the opportunity of examining the intestines 

 of a young Elephant -Seal (iW«o-o?Vi/««.s leoninus). By the kind- 

 ness of my colleague, Mr. D. Seth-Smith, I am able to reproduce 

 as text-tig. 27 a photograph of the intestinal tract removed from 

 the body and laid out to display its pattern. For this purpose, 

 owing to the simplicity of the gut in this group and the absence 

 of secondary connections, it was necessary only to sever the 

 primitive mesentery that stretches from the duodenum to the 

 rectum. 



As in the Walrus, the duodennl region is not sharply marked 

 off from Meckel's tract. Tlie latter is of even calibre, and is 

 thrown into exti-emely numerous minor folds arranged so as 

 almost completely to surround an oval expanse of mesenter3\ 

 Its length is enormous. The Elephant-Seal that I examined 

 measured six feet nine inches from the tip of the snout to the 

 tip of the tail : the small intestine measured with the tape, when 

 the mesentery had been detached, one hundred and seventy-five 

 feet six inches ; the hind-gut was onh' two feet four inches long. 

 "When it has nearly reached the level of the duodenum, the 

 distal limb, without any change of calibre, bends sharply round, 

 and after a course of nearl}' a foot, suddenly changes in calibre. 

 At this point there is nothing that can be called a ca?cum, and it 

 is doubtful whether the change from fore-gut to hind-gut can be 

 placed accui'ately. If it is where the gut expands, then the position 

 is quite abnormal amongst mammals : if, as in the Walrus, it is 

 at the extremity of the recurrent limb of the pendant loop, then 

 the sudden change of calibre in the course of the hind-gut, is also 

 unusual. The hind-gut, after widening, bears an enlarged simple 

 loop, which in the photograph is represented in an unnatural 

 position ; the distal end of the rectum was bent forwards to bring 

 it into the picture. It appears to belong to the region distad of 

 the pendant loop, and is an ansa coli sinistra. 



The gut patterns of the Walrus and of the Elephant-Seal do not 

 difler notably from those of the Sea-Lion and of the true Seals 

 that I have' already described (Mitchell, 1905, p. 493, fig. 32). 



