Practical Course. ll 
of the chamber to supply blood to the posterior organs of 
the body. 
Now turn to the abdominal cavity and endeavour to make out the 
vessels which unite to form the portal vein, which returns the blood from 
the digestive tract and spleen to tlie liver, where it passes through a 
series of capillaries before joining the posterior vena cava, The chief of 
these vessels are—(1) the lineogastric vein, which returns the blood 
from the stomach and spleen; (2) the duodenal vein, which returns the 
blood from the duodenum ; and (8) the anterior and posterior mesenteric 
veins, which return the blood from the whole of the intestine and rectum. 
These veins are best seen in a fresh specimen; the important point to 
remember about them is that the blood from the whole length of the di- 
gestive tract returns to the liver. 
Free the coils of the digestive tract by cutting through the membran- 
ous mesentery by which it is supported. Straighten out the intestine. 
Trace up the narrow tube (csophagus) which passes through the dia- 
phragm and serves to convey the food from the mouth into the stomach. — 
Observe that the whole digestive tract is merely a winding tube which 
connects the mouth in front with the anus bebind, and notice the fol- 
lowing portions of it :— E 
(1) The narrow cesophagus. 
(2) The expanded stomach. 
(3) The narrow portion (duodenum) which leaves the right side of 
the stomach and receives in front the bile duct from the 
liver, and behind the duct from the pancreas, which is a 
gland situated in the loop formed by the duodenum and is 
very small in the palm squirrel. 
(4) The small intestine, which is the narrow winding portion of the 
tube between the duodenum and a large blind sack-like 
outgrowth known as the cecum. 
(5) The remainder of the tract consist of the colon and rectum, 
where the tube is somewhat wider. The rectum opens at 
the anus behind. 
Cut away the whole of the digestive tract, also the liver, diaphragm, 
heart, and Jungs, with scissors. The dorsal aorta can now be readily 
traced down the back, immediately above the vertebral column on the 
left side. Dissect it out as far as possible, noticing the branches that it 
gives off in its course. 
Dissect away the muscles of the shoulder and hip, so as to see the 
large nerves (brachial plexus) which supply the fore-limb, also the large 
nerves (lumbo sacral plexus) which supply the hind-limb. These nerve 
plexi are formed in each case by the union of several nerves which issue 
from the spinal cord, but it will not be necessary to trace them to 
their origins. 
