| 1. | Mouth. | 13. | Rectum. |
| 2. | Pharynx. | 14. | Anus. |
| 3. | Œsophagus. | 15. | Left kidney and ureter. |
| 4. | Diaphragm. | 16. | Bladder. |
| 5. | Spleen. | 17. | Urethra. |
| 6. | Stomach (left sac). | a. | Hard palate. |
| 7. | Duodenum. | b. | Tongue. |
| 8. | Liver (upper extremity). | c. | Soft palate. |
| 9. | Great colon. | d. | Trachea. |
| 10. | Cæcum. | e. | Pulmonary artery (divided). |
| 11. | Small intestine. | f. | Heart. |
| 12. | Floating colon. | g. | Posterior aorta. |
CHAPTER IV.
SPLANCHNOLOGY.
Study of large interior organs in any of the four great bodily cavities especially those in the abdomen.
Digestive Organs of the Horse.—The digestive organs comprise the alimentary canal and the accessories by which the alimentary matter is received and subjected to specific actions, which adapt it for purposes of nutrition. Digestion, therefore, embraces the collective operations and changes which the food undergoes in the alimentary canal.
The whole digestive track from the mouth to the anus which is situated just below the tail, is sometimes called the alimentary canal.
The mouth is an oval cavity at the commencement of the alimentary or digestive canal. In front of the mouth are the lips, one above and one below; at the sides are the cheeks. The mouth is lined with what is known as the mucous membrane, in which are several small openings, from the glands, which are situated about the mouth. Through these the saliva is poured. On the upper part of the mouth the mucous membrane is thrown into ridges, or folds, from 18 to 20 in number. This is a point of importance in connection with bleeding a horse with lampas. It is never safe to bleed back of the third bar because there is a large artery which runs down through the roof of the mouth and enters the hole in the bone just before it reaches this bar. The tongue, which has the chief nerves of the sense of taste, is situated in the mouth; this organ also has a very important part to perform in masticating the food and mixing it with saliva. The teeth, which also take a very active part in the masticating of food, are dealt with under the heading of “Teeth.”
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.