anatomy of the three-toed sloth. 161 



The Stomach. 



The external appearances have been described by Cuvier (3), 

 Meckel (7), Cams (2), Otto, Boulart, and Pilliet "(9), and the 

 internal appearances of the stomach of B. cuculUger liave been 

 described by Rapp (10) and Klinckowstrom (6). Many details 

 can be added, however, to their accounts. Moreover, the internal 

 appearances and the relative positions of the various compart- 

 ments are different in B. tridactylus and B. cuculliger or gularis. 



The stomach heel in my specimen is unusual, for the position of 

 the pancreas is peculiar ; that organ is contained within the 

 duodenal loop and none of it lies dorsal to the stomach. Again, 

 the stomach bed does not contain the spleen, for the latter, in 

 Sloths, lies on the right side of the pylorus. The kidneys lie i'ar 

 back in the abdomen, and the suprarenal capsules are separated 

 from them, but lie in the normal position. Consequently, the 

 adrenal bodies are dorsal relations of the stomach, but the 

 kidneys are posterior. In my sjDecimen the stomach has the 

 following relations : — 



Anterior — ^liver and diaphragm. 

 Posterior — intestines and kidneys. 

 Ventral — ventral abdominal wall. 



Dorsal — vertebral column, main blood-vessels, suprarenal cap- 

 sules, root of the mesentery. 

 To the left — abdominal parietes. 

 To the right — spleen, pancreas, duodenum. 



These peculiar arrangements make the disposition of the 

 peritoneum, which is described below, noteworthy. 



In my specimen the gravid uterus touched the greater 

 curvature. 



Divisions of the Stomach. — I agree with Klinckowstrom's 

 division of the stomach into three groups of compartments : — 



1. The Paunch, or Fundus Stomach, with its crecal appendage 

 (Plate II. A, C and B, i.i.i.). 



2. The Cardiac Stomach with tlu'ee divisions (Plate II. A, D 

 and II. B, d. c. d, 2). 



.3. The Pyloric Region composed of two parts — glandular and 

 muscular (Plate II. B 3). 



In B. tridactylus the main divisions, and most of the sub- 

 divisions, can be distinguished on the surface. The paunch is 

 marked off from the cardiac stomach by a notch on the left part 

 of the greater curvature (Plate II. A, a) and a faint ridge running 

 from the notch to the base of the cfecal appendage. This ridge 

 marks the anterior limit of a number of fissures running forward 

 from the greater curvature, but these are not so deep as in 

 B. cuctdliger. The cai-diac stomach is easily marked out from the 

 pylorus ; it is capacious and has thin walls, but the j^ylorus is a 

 thick, muscular, U-shaped tube. 



Proc. ZooL. See— 1921, Ko. XL 11 



