712 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 coeliac 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 Camelide), 
but many good observers 
describe spherical or cup- 
oe ee ie shaped or bell-shaped red 
ral ih Ce ote blood corpuscles. It is not 
Claude Bernard. certain how far these shapes 
P., Pyloric end of stomach; g.d., gall- Aare normal. The four-cham- 
bladder with bile duct and hepatic bere heart lies in the thoracic 
ducts; .d., pancreatic duct. ; 
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 vene cave, 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 chordz 
tendinez attached to papillary muscles projecting from the 
wall of the ventricle). 
