Dif/estive Organs of the Ox and Sheep. 
43 
pancreatic joins the biliary tube before the latter penetrates the 
duodenum, and in tlie horse and the pi<; the two enter close to 
each other. These facts are diflicult of explanation, but of great 
importance to the comparative physiologist. It is also worthy of 
note that some animals possess a receptacle for the bile, called 
the gall-bladder, d, while it is wanting in others. As a rule it is 
not met with in the pachydermata, of which fact the horse is an 
example, and the pig an exception. The carnivora possess it, and 
it is generally present in the ruminantia, but is wanting in the 
camel and the deer tribe. 
As before stated, the secretions of the liver and pancreas pro- 
duce a separation of the chyle from the ingesta ; this is precipi- 
tated upon the villous membrane of the intestines, from whence 
it is removed by a particular set of absorbent tubes, the lacteals, 
into the general circulation. These vessels are represented as 
lines crossing the mesentery (figs. 9 and 10) ; they receive their 
name from the milky appearance of the chyle. In their course 
many of them enter the mesenteric glands (see g, figs. 9 and 10), 
where tlie chyle is further elaborated. The lacteals unite with 
each other and ultimately form three or four ducts, which empty 
themselves into a cavity situated near to the spine, termed the 
receptaculum chyli. From this receptacle the fluid is conveyed by 
a canal, which, passing through the chest, receives the name of 
the thoracic duct, into the left jugular, or sometimes into the left 
axillary vein, where it is commingled with the blood. 
We observed at the commencement of this lecture that the 
blood carries by its circulation the elements of reproduction and 
nutrition to every part of the body ; it is therefore evident that it 
must suffer loss, and we have now seen how this is compensated by 
the food on which the animal subsists. To preserve health it is of 
the first importance that good and nutritious diet, such as will 
neither cloy the appetite nor impair the digestive process, should 
be given to all animals, for, without due attention to this, disease 
will be a certain result. The wants of the system are recognised 
by two sensations, hunger and thirst ; the first gives evidence of 
the loss of nutrient matter, the second of fluid. Hunger may be 
said to have its seat in the stomach, and thirst in the throat. 
Where health is the object, both should be satisfied, but neither 
indulged. Excess of nutriment accumulates in the form of fat, 
but fat animals are on the brink of disease. The inhalation of 
pure air is of equal importance to the taking of proper food, for 
the blood constantly requires purificaticm as well as supply ; this is 
effected by respiration, which, like digestion, is also a chemical 
process. We must not, however, enter upon this subject, but 
return to our description of the intestines. 
The intestinal canal, although continuous, is divided into six 
