7 I2 



MAMMALIA. 



tubes into the pancreatic duct which opens into the 

 duodenum. 



The mesentery, which supports the alimentary canal, is a 

 double layer of peritoneum reflected from the dorsal abdo- 

 minal wall. 



The dark red spleen lies behind the stomach. In the 

 mesentery, not far from the top of the right kidney, lie a 

 pair of cceliac ganglia, which receive nerves from the thoracic 



sympathetic system, and give 

 off branches to the gut. 



Vascular system. The 

 blood of Mammals contains, 

 as in other Vertebrates, red 

 blood corpuscles (erythro- 

 cytes) and white blood cor- 

 puscles (leucocytes), but the 

 former are non - nucleated 

 except in their young stages. 

 It is probable that the nuclear 

 material becomes diffused 

 through the cell. They appear 

 as slightly biconcave circular 

 discs (elliptical in Camelidae), 

 but many good observers 

 describe spherical or cup- 

 shaped or bell -shaped red 

 blood corpuscles. It is not 

 certain how far these shapes 

 are normal. The four-cham- 

 bered heart lies in the thoracic 

 cavity between the lungs. It 



is surrounded by a thin pericardium, and immediately in 

 front of it there lies the soft thymus, which is larger in the 

 young than in the adult animal. 



By two superior venae cavae, and by the inferior vena 

 cava, the venous blood collected from the body enters the 

 right auricle. Thence the blood passes into the right 

 ventricle through a crescentic opening, bordered by a 

 threefold (tricuspid) membranous valve (worked by chordae 

 tendineae attached to papillary muscles projecting from the 

 wall of the ventricle). 



FIG. 390. Duodenum of rabbit. 



From Krause, in part after 



Claude Bernard. 

 P., Pyloric end of stomach ; g.b., gall- 



