INTESTINAL TRACT OF MAMMALS. 217 



I did not find it in Traguloidea or Tylopocia, but it is present in 

 most of the true ruminants. Dr. Beddard describes it as 

 practically absent in Madoqua and as spirally twisted in Moschus. 

 In a Musk-deer that I examined, it was long, but showed no 

 trace of a spiral. 



Distad of the postcsecal loop, the recurrent limb of the pendant 

 loop is disposed in a spiral coil characteristic of the true 

 ruminants and equally well marked in the T^dopoda.. It is this 

 region of the gut that forms a set of large coils in the Hippo- 

 potamidse, and a spiral arranged to form a solid conical mass in 

 the Suidae. In the Traguloidea, as has been already described 

 by me (Mitchell, 1 905) and confirmed by Beddard (Beddard, 1909), 

 the colic spiral is very small and is not flattened. In the 

 communication just cited, Dr. Beddaid describes a somewdiat 

 similar very small spiral in the minute antelopes of the genus 

 2Iadoqua, but in Tylopoda and all the true ruminants, except 

 Madoqua, of which the alimentary canal has been described, the 

 spiral is nearly flat and consists of a var3'ing' number of tiu-ns. 

 This flat s]jii"^lj i^i the undisturbed condition, is folded against 

 the mesentery that supports Meckel's tract in the fHshion that 

 the contiguous pages of a closed book touch one another. The 

 spii-al is much smaller than the expanse of the tract, and, in the 

 undisturbed condition, it appears to be surrounded by the curved 

 line formed by the minor loops of the tract. This arrangement, 

 which is familiar to anatomists, is well represented in some of 

 the figures given by Dr. Lbnnberg and Dr. Beddard (e. g. Lonn- 

 berg, 1907, flg. 4 ; Beddard, 1909, text-fig. 14). The spiral coil is 

 composed of a long narrow outgrowth of the hind-gut, rolled up 

 from its apex, and the primitive mesentery belonging to the 

 spiral has coalesced with the mesentery supporting Meckel's 

 tract in so complete a. fashion that '' short-circuiting " blood- 

 vessels appear to supply these two vei-y difierent regions of the 

 intestine indifferently. Moreover, especially where the coil is 

 large, secondary bands of fibres unite the coil firmly with the 

 intestinal region against wdiich it is pressed. Unfortunately, 

 Dr. Lonnberg does not appear to have considered these primary 

 and secondary attachments, and Dr. Beddard s figui-es (e. g. 

 Beddard, 1909, text-fig. 15) do not distinguish between the five 

 different sheets of membrane to which the connections between 

 adjacent portions of the spiral coil may be referred, that is to 

 say, the double layer of the pi'imitive mesentery of Meckel's 

 tract to w^hich the spiral coil is adherent, the double layer of the 

 primitive mesentery of the coiled loop that forms the spiral, and 

 the adventitious layer of connective-tissue fibres which assists in 

 holding the coil in its place. This absence of distinction would 

 be of no moment if the figures were, like my diagrams, intended 

 merely to represent the general morphology of the gut-pattern, 

 but it is another matter when the attempt is made to distinguish 

 between species and species by the characters of the spiral coil. 

 Dr. Lonnberg, who has made such an attempt, has devised an 



