INTESTINAL TRACT OF MAMMALS. 511 



similar to that in Ateles ; but the duodenal loop is less distinct, the caecum is relatively 

 a little larger and does not taper, whilst there is no external indication of a second 

 caecum. The hind-gut is practically identical with that of Ateles in its arrangement. 



In Ouacaria ruMcwida there is no distinct duodenal loop. Meckel's tract is 

 relatively much longer and is composed of irregular loops very closely set together. 

 The single caecum is capacious, tapers to a point, and is slightly spirally twisted. 

 The hind-gut, which is relatively short, consists of a well-defined colic loop passing 

 insensibly into a straight rectal portion. The arrangements of the mesenteric veins 

 are much as in Ateles. 



Sub-Order CATARRHINA. 

 Family Cercopithecidje. 



Sub-Family CERCOPiTHECiNiE. Gercopithecus niger, 0. stairsi, C. werneri 

 (fig. 44, p. 512), Macacus arctoides, M. rhesus (fig. 49, III, p. 521). 



In these Monkeys the duodenal loop is seldom distinct. Meckel's tract consists of 

 a number of simple minor loops and a terminal unconvoluted portion suspended at the 

 periphery of a nearly circular expanse of mesentery, the terminal portion of which, 

 however, acts also as a mesocolon. Meckel's tract as a whole is relatively rather short, 

 but is relatively longer in most Cercopithecinae, and especially in the Hacaci, than 

 is represented in fig. 44. The caecum, which is always present, varies considerably. 

 The condition shown in fig. 44, where the caecum is rather large, capacious, and 

 slightly curved, I have found in other species of Cercopithecus, but it is usually 

 relatively shorter and wider. The hind-gut is always long and extremely capacious. 

 It displays first a portion continuous with the caecum ; then a very large colic loop 

 always thrown into a number of wide minor loops, the last of which may be regarded 

 as a sigmoid flexure and which passes into the relatively short, straight rectum. 



The anterior mesenteric vein curves round the Meckelian mesentery and receives 

 irregular branches from the minor loops, a large coscal vein, and one or more vessels 

 from the proximal portion of the hind-gut. The posterior mesenteric vein forms a 

 complex branching system which drains both colon and rectum. 



Sub-Family SEMNOPmiEciNiE. Nasalis larvattis. 



In this sub-family the duodenum appears not to be separate. Meckel's tract is 

 relatively very much longer than in the Cercopithecinae, its minor loops being more 

 numerous, closer set, and longer, but the general pattern formed is similar. The 

 caecum is relatively smaller and is conical, but shows no trace of vermiform appendix. 

 The hind-gut, except that in proportion to the fore-gut it is shorter, is similar 

 in its differentiation. The mesenteric veins repent the arrangement found in the 

 ( lercopithecinae. 



9 v >) 



