INTESTINAL TRACT OF MAMMALS. 



187 



(Mitchell, 1905), and the paired condition is normal in some 

 Edentates, Hyi'acoidea, and Manatus. 



The hind-gut of mammals differs notably from that of birds, 

 inasmuch as it tends to be drawn out into specialised loops 

 forming patterns charactei-istic of dijfferent groups. A rather 

 different nomenclatui'e has been applied to these minor loops of 

 the hind-gut by different anatomists ; I propose in this communi- 

 cation, following, I believe, the more exact of my predecessors, to 

 designate these loops by their morphological position. The liighest 

 point of the recurrent limb of the pendant loop, where it bends 

 round to pass into the pi'imitive straight hind-gut, represents 

 what in many mammals forms the transverse colon ; a loop of 



Text-fisfure 1. 



Mes. 



Diagram of the primitive Mammalian Gut-pattern. 



A. In a young embryo. B. In a simple adult. 



S. Cut junction with the stomach. R. Cut distal extremity of the rectum. 

 Mes. Dorsal mesentery. M. Attachment of umbilical cord, position of 

 Meckel's diverticulum. C. Csecum. 1-2. Duodenal region. 2-3. Meckel's 

 tract. 3-4. Hind-gut, i. e., large intestine and rectum. 



the hind-gut to the right, or proximad, of this is an ansa coli 

 clextra ; a loop to the left, or distad, of this forms an ansa coli 

 sinistra. The angle between the ascending colon and transverse 

 colon in human anatomy, on this nomenclature, might be called 

 a vestigial ansa coli clextra ; the corresponding angle, where the 

 transverse colon passes into the descending colon, would be a 

 vestigial ansa coli sinistra. A loop of the recurrent limb of the 

 pendant loop, proximad of these and close to the cfecum, may be 

 called a postcfecal loop or paractecal loop. 



It will be seen that my conception of the primitive mammalian 

 gut differs in two respects from that presented by Dr. Beddard 

 (Beddard, 1908, p. 591). First and most important, I regard the 



