221; 



DR. P. CHALMERS MITCHELL ON THE 



Rails and Cranes. The duodenum is normal ; Meckel's tract displays the loops which I 

 have marked "a" and "6" pi-ecisely as in the Rails, and "6" the axial loop bears 

 a large diverticulum on its distal limb. The posterior portion of the tract differs : in 

 place of "c," tlie third loop, and of the normal supra-duodenal loop, there are a set 

 of irregular small loops. The caeca are short but wide and in the natural condition 

 contain faecal matter. The rectum is short, wide, and straight. I am disposed to think 

 that the type ia Aramiis is more archecentric than the types displayed by the Cranes and 

 Rails. Although the axial loop with the diverticulum on its lower limb is character- 

 istically Ralline, the general conformation of Meckel's tract is much more like the 



Kg. 43. 



Tn 



Intestinal Tract of Aramus sMlopaceus. Lettering as in fig. 41. 



archecentric condition, and this similarity is increased by the moderate length of the 

 caeca and the absence of a specialized supra-duodenal loop. I think it is more probable 

 that the long caeca of the Cranes and Rails are an apocentric modification than that the 

 relatively shorter caeca of Araimis are pseudocentric degenerations, for, as I hope to show 

 later, in the vast majority of cases where the caeca are obviously degenerate, the 

 "bridging" factor or factors from the duodenal vein, which originally drained them, 

 persist to drain a specialized supra-duodenal loop, and there is no trace of this in 

 Aramus. 



A 



