INTESTINAL TRACT OF MAMMALS. 197 



Dr. Mackenzie had ascertained to consist of lymphoid tissue. On 

 opening the gut, each pouch was seen to have a wide aperture 

 towards the hind-gut, the blind apex pointing forwards towards 

 the apex of the c£ecum. These pouclies suggest strongly the 

 presence of an original puiv of cseca, the apices of which have 

 fused to form the prodigiously long cjecum. Tlie cjecum is 

 supported by a mesentery superficial to the primitive mesentery 

 and suspending it to the duodenal region. It is represented 

 as severed in text-fig. 8, and the cut ends of the csecal vein 

 are marked at X.X. 



Immediately distad of the ctecum is an enormous colic loop, 

 very wide in calibre and susjiended at the periphery of an 

 oval expanse of the primitive mesentery, continuous with the 

 mesentery suspending Meckel's tract. This portion of the hind- 

 gut must be taken as an outgrowth of the recurrent limb of the 

 pendant loop, and is therefore an ansa coli dextra. It is 

 followed by a stout-walled portion of the gut, rather smaller 

 in calibre, and curving round from the colic loop to the rectal 

 portion. It is at this point that the intestinal tract returns to 

 the dorsal middle line, and a veiy strong secondary " ligament " 

 attaches it to the omentum and to the duodenal region. Distad 

 of this the calibre of the gut is again reduced, and the rectal 

 portion is enormously expanded and thrown into a regularly 

 placed set of minor loops attached to a meso-rectum which is 

 more semicircular in shape than in the diagram. This expanded 

 portion of the rectum must be regnrded as an ansa coli sirdstra. 



The gut of the Koala, in relation with the diet of leaves, is very 

 long and very capacious. It is divided into four regions, nearly 

 equal in capacity, and each "bunched up" on an expanse of 

 miesentery. To display them on a flat diagram they had to be 

 slightly distorted, as well as unfolded. Comparison of the figures 

 of the gut-patterns of other marsupials, however, shows that in 

 the Koala there is only an exaggeration of familiar features, 

 and the pattern resembles that of the Wombat very closely. It 

 is interesting to notice that the gut-patterns of the ruminants, 

 in which also the whole gut has become much enlarged in 

 correlation with the diet, are strikingly difi"erent. 



Family Macropodidte. Dendrolagus ursinus (text-fig. 9). 



The duodenal region passes insensibly into Meckel's tract, 

 the latter being thrown into minor folds, which are more closely 

 set than in the figure. The example that I dissected was very 

 joung ; it was born in the Society's Gai'dens, but died before it 

 had left the marsupial pouch of the mother. The coils of 

 Meckel's tract were closely packed, and in the undisturbed 

 condition displayed tlie double spiral represented in the drawing 

 (text-fig. 9, 1). The unconvoluted distal end of Meckel's tract 

 was constricted as it entered the dilated hind-gut between a 

 normal but rather .small CEecum (text-fig. 9, C.) and a smaller 



