-216 



DR. P, CHALMERS MITCHELL ON THE 



mesenterial expanse. These minor loops cease towards the apex 

 of the original pendant loop, tlie first portion of the recurrent 

 limb being nearly straight, until it bends over to enter the 

 caecum. The ctecum is alwaj's present and is capacious, but not 

 of great relative length. In Moschus, as an exception, it is very 

 long a,nd narrow. Its cavity is a, forward continuation of the 

 cavity of the hind-gut. I have already shown (Mitchell, 1905, 

 p. 518) that the relation of the ileum to the caecum and hind-gut 

 -often presents appearances best explained on the supposition that 

 the normal caecum is the surviving member of an original pair of 

 caeca. I figured a mass of lymphoid tissue in the case of Gazella 

 marica, so situated that it seemed to represent a degenerate 

 second csecum. In an example of Moschus moschifents that I 

 have examined since, the same portion of the gut was occupied 

 by a distinct caecal pouch, the aperture to which was marked off 

 by a V-shaped lidge. The iliac aperture lay on a raised lip 

 between this and the wide aperture of the true caecum. 



'lA. CzA 



Ileo-Cifical region in MoscJms moscliiferus. 



■Q. Cut CEBCum. H. Cut hind-gut. S.I. Cut small intestine. W. " Window " cut 

 in the wall of the ileo-cwcal region. I. A. Aperture of ileum to csecum and 

 hind-gut. C. 2. Second Cfecum. C. 2 A. Aperture of second Cfficum to hind-gut 

 protected by V-shaped I'idge. 



I can suggest no explanation of this arrangement other than 

 that the second membei' of a primitive pair of cfeca is less 

 vestigial than is usual. 



On leaving the caecum the hind-gut has a much smaller calibre 

 than is usual in mammals, being little wider than the distal end 

 of the ileum. The length and peculiar arrangement of the 

 hind-gut form the most characteristic feature of the intestinal 

 pattern of this group of Artiodactyles. Immediately distad of 

 the cajcum, there is usually a rather narrow single loop, which 

 I called the postcecal loop (Mitchell. 1905, fig. 22, P.O.L.). 

 Dr. Lbnnberg (Lonnberg, 1907, p. 241) objects to this name, 

 inasmuch as he himself (Lonnberg, 1903, p. 7) had termed a 

 similar loop in various ruminants the ansa j^'^'oximalis. Dr. 

 Beddard in a later paper (1909, p. 181) calls this loop the ansa 

 paraccecalis. The name is of little importa,nce, but paiacaecal or 

 postcaecal describes its position bettor Its presence is variable ; 



