1908.] ANATOMY OF A FROG. 33 



of the small intestine, that immediately following upon the pyloric 

 constriction corresponding to the duodenal looj) of Rana, is very 

 short, about 5 mm. long (in the smaller male specimen), and 

 directed rather forwards and parallel with the fetomach as in 

 Rana. It is of narrow calibre, about that of the pyloric process 

 of the stomach. This passes into a middle section of the small 

 intestine, the bore of which is quite twice that of the preceding 

 part, and which forms therefore a very wide tube. This is no case 

 of accidental dilatation, for the same structure was apparent in both 

 examples, and the appearance of the swollen region of the intestine 

 was quite different from the region in front of and behind it. 

 Internally its mucous membrance is raised into transverse folds, 

 which have not the watch-pocket shape of the corresponding folds 

 in the intestine of Rana^ but are thin wavy folds running right 

 round the lumen. This wider portion of the small intestine passes 

 into a narrow portion again, which is of greater length and of not 

 greater calibi"e than the beginning of the duodenum. This ojoens 

 suddenly by a slightly projecting os into the very wide but not 

 very short large intestine. 



The end of the colon, into the pear-shaped anterior section of 

 which the ileum opens, bulges equally all round the ileum ; that 

 is to say, there is no unilateral ctecum. Shortly after the entrance 

 into it of the small intestine the colon diminishes in its width and 

 remains at about the same calibre to the anal apertures. That 

 is to say, of course, the cloaca is no wider than the antecedent 

 colon. The cloaca is of considerable length, and is shown in the 

 figure on p. 20 (text-fig. 4). It occupies the whole of the sjiace 

 lying between the tip of the coccyx and the rather distant end of 

 the body. Being, as it is, in this exposed situation and covered 

 only by the skin, it would appear to be rather susceptible to 

 injury from pressure upon the dorsal sui-face of the body. It is, 

 however, protected from such injury, it may be supposed, by a 

 thick covering of muscle upon the dorsal surface. This is obviously 

 divided into two longitudinal bands by a furrow, and this arrange- 

 ment becomes clearer still when the tube is cut across. This 

 muscle arises, partly at least, from the tip of the urostyle and 

 corresponds, I imagine, to the compressor cloacce oiRana *. There 

 are also two very tiny muscular slips attaching the end of the 

 cloaca to the skin just above ; they are also shown in the figure 

 referred to. 



§ Posterior Ly^mpli-hearls . 



These organs are so extraordinarily developed in Breviceps that 

 they require a section to themselves for their adequate descrip- 

 tion. The general topography of their neighbourhood may be 

 first described, as it differs greatly from that of Rana and is in 

 relation to the large size of these sacs in Breviceps. As already 

 mentioned, the thighs of this species are enclosed within the 



* Ecker's 'Anatomy of the Frog,' Haslam's Translation, p. 348. 



Proc. Zool. Soc— 1908, No. III. 3 



