SALIVARY GLANDS.--These glands secrete the saliva that is poured into the mouth while the animal is eating. There are only three pairs of much importance. One large pair, one on each side of the throat below the ears, known as the parotid glands, fill up the space between the jaw bone and the neck. This pair has tubes passing around and under the lower jaw and up into the cheek muscles entering the mouth opposite the fourth molar tooth. These tubes, known as steno’s ducts are about an eighth of an inch in diameter and convey the saliva from the glands into the mouth. The next pair are situated under the pair just mentioned. Their tubes enter into the bottom part of the mouth. The third pair are situated under the tongue, one on each side. They pour their secretion into the mouth by several small openings near the front under the tongue. This can be seen by examining the under surface of the tongue closely. This is very important fluid in connection with the digesting of the food. The gullet is a cavity situated just back of the mouth. It is chiefly made up of muscles which perform the act of swallowing the food. It is lined with the continuation of the mucous membrane of the mouth. The oesophagus, or the continuation of the gullet, is a tube extending from the gullet to the stomach, and is used to convey the food to that organ. It is made up of two coats, the muscular and the mucous. The former contains fibers which, when once the food enters the tube, contract behind it, forcing it down to the stomach. Its lining is a continuation of the mucous membrane of the mouth and the gullet. In tracing the oesophagus or tube down the neck from the gullet, note that it passes down the left side of the neck, entering the thoracic, or chest cavity, between the lungs over the heart through the large muscular curtain known as the diaphragm, then enters the stomach an inch or two after passing the diaphragm.