AXATOMY OF THE THREE-TOED SLOTH. 173 



two halves is the anterior part of the lesser sac (text-fig. 13, B), 

 which opens into the Spigelian Recess of the liver. 



The Mesentery . 



The mesentery has an attachment from liver to pelvic floor 

 which begins anteriorly to the right of the mid-line, but passes 

 posteriorly and to the left to reach it. It is composed at first of 

 the suspensory ligament, and its free edge is attached first to the 

 diaphragm, then along the posterior surface of the liver 

 (Plate II. A, n). Its free edge then, containing the common bile- 

 duct, runs from the portal fissure to the duodenum. Finally, it 

 follows the intestine to the pelvic floor. It has attached to it 

 the layers of the great omentum. It sends a tubular sheath 

 round the oesophagus (text-fig. 13, B, e). 



The stomach is attached to it anteriorly by the lesser omentum, 

 and to the right by the connection round the duodenum (text- 

 fig. 14, B). 



No peritoneal bands connect the duodenum to the colon. 



Dr. Chalmers Mitchell (8) and others have described the peri- 

 toneum from duodenum to anus, and the only fact which I have 

 to add to their accounts is the prominent ridge produced in the 

 mesentery by the posterior mesenteric vessels. 



The Suprarenal Capsules. 



The left capsule is flat and ovoid and measures :— 



-Length 1-8 cm. 



Width -75 



Thickness -35 ]] 



The right capsule, as is shown by the following figures, is 

 longer, narrower, and thicker : — 



Length 2 cm. 



Width -6 



^ ii 



Thickness -5 



Both lie a considerable distance anterior to their corresponding 

 kidneys. On section the right capsule shows a round cortex and 

 medulla, but these are long in the case of the riffht one (text- 

 fig. 11, E). V " 



The Thoracic Organs. 



Burne (1) and Rapp (10) have described the heart and large 

 vessels, but the branches of the aortic arch in my specimen are 

 different to their accounts. It gives off from right to left the 

 innominate, left subclavian, and three intercostal arteries ftext- 

 fig. 15, B). * • 



The posterior border of the arch is connected to the left 

 pulmonary artery by a very prominent ligamentum arteriosum ; 

 this measures 1 cm. long and 2 mm. wide, but is quite 

 impervious. 



