58 
THE VETERINARY SCIENCE 
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 as large as straws 
and convey the saliva from the gland into the mouth. The 
next pair are situated under the pair first mentioned. Their 
tubes enter into the bottom part of the mouth. The third 
pair are siuated 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 exam- 
ining closely. This is a very important fluid in connection 
with the digesting of the food. 
3. The Gullet is a cavity situated just behind 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. 
4. The Oesophagus, or the continuation of the gullet, is 
a tube extending from the gullet to the stomach, and is used 
to carry the food to that organ. It is made up of two coats, 
the muscular and the mucous. The former contains fibres 
which, when once the food enters the tube, contract behind 
it, forcing it along to the stomach. Its lining is a continu- 
ation of the mucous membrane of the mouth and gullet. In 
tracing the 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 dia- 
phragm. 
5. The Stomach. — This organ is very small in the horse 
in comparison with that of the ox. It holds only about four 
gallons, and is situated just behind the curtain which sep- 
arates it from the lungs. It lies mostly to the left side. The 
walls of the stomach are composed of three coats. That on 
the outside is called the serous membrane, a name applied to 
membranes which line closed cavities, such as the abdominal, 
or belly cavity. The inside lining is a continuation of the 
mucous membrane lining the organs before mentioned. The 
lining in the left part of the stomach or the part where the 
food is prepared for digestion is the same color as that of 
the mouth. The lining of the right part of the stomach, 
which is the true digestive part, is of a deep red color re- 
sembling velvet, and when placed under a microscope has the 
