INTESTINAL TEACT OF MAMMALS. 4S7 



the example I examined as in that figured by Garrod, but is well seen on opening the 

 cavity. It is obviously the same kind of condition as occurs in the Hare, and is to be 

 explained by the supposition that originally the caeca were paired. The hind-gut is 

 divided into a colic region consisting of two loops closely twisted together, and showing 

 a spiral folding, most unusual in this region in the Rodents, and recalling superficially 

 the spiral coil of Artiodactyles. It is essentially dissimilar, however, as it is formed of 

 two loops folded together. The rectum is very long, its proximal portion being 

 considerably expanded. 



The arrangement of the veins is normal. 



In the Patagonian Cavy {Bolichotis jpatachonica) there is no distinct duodenum. 

 Meckel's tract is very long, and consists of much contorted minor loops at the edge of 

 an elongated oval mesentery. The csecum is extremely long and capacious and is 

 spirally twisted, the twisting involving the proximal portion of the hind-gut. The 

 latter consists of a colic region, the first loop of which is involved in the coiling of the 

 caecum, the second being large and extremely irregular. The rectum is very long and 

 displays a large series of minor loops. The arrangement of the mesenteric veins is 

 essentially similar to that in the Capybara. 



Sub-Family Chinchilluxe. Lagostomus trichodactylus. 



In the Viscacha there is no distinct duodenal loop. Meckel's tract is long, and 

 consists of a series of minor loops and a long straight recurrent portion suspended at 

 the periphery of an expanse of mesentery nearly circular. The caecum is extremely 

 capacious and sacculated. The hind-gut consists of two very long, rather simple loops. 

 The rectum is greatly expanded, consisting of a series of proximal loops and a straight 

 distal portion. 



The anterior mesenteric vein curves round the Meckelian mesentery and receives a 

 large vein which drains the caecum and the first loop of the hind-gut and, separately, 

 a vein from the second colic loop, whilst it is joined near the edge of the mesentery by 

 a normal posterior mesenteric vein. 



Sub-Family Capromyid^e. Capromys pilorides. 



The pattern of the intestinal tract of this animal is extremely like that of the 

 Guinea-pig. The caecum is rather less sacculated and is relatively longer, the spiral 

 twist being rather greater. Otherwise the diagram given for Cavia (fig. 28, p. 485) 

 might equally well represent Capromys. 



Sub-Families Octodontid,e and Chenodactylid^e. 

 I have not had the opportunity of examining members of these sub-families. 



3t2 



