DISEASES OF THE NERVOUS SYSTEM. I03 



Medulla Oblongata. This is the prolongation of the spinal cord, 

 extending from the spinal cord to the pons (bridge) Varolii. 

 This part of the brain is very large in the horse; it is pyramidal in 

 shape, the narrowest part joining the cord. 



Spinal Cord. This occupies the cavity of the backbone. It ex- 

 tends from the brain down to the last vertebra. It is protected by the 

 same membranes as the brain, but in the brain the gray matter is on the 

 outside, while in the spinal cord the gray matter is within. It is divided 

 into halves and these again subdivided into two parts. It contains 

 two nerves of motion and two of feeling. The nerves of motion are the 

 ones which carry the orders of the mind to the different organs, while 

 the nerves of feeling bring back impressions which they receive. 



Spinal Nerves. These are forty-two or forty-three in number, 

 arise each by two roots, a superior or sensory and an inferior or motor. 

 The nei"ves originating from the brain are twenty-four in number, and 

 arranged in pairs, which are named first, second, third, etc., counting 

 from before backward. They also receive special names, according to 

 their. functions, or the parts to which they are distributed, viz: 



, I. Olfactory. 5. Trifacial. 9. Glosso-Pharyngeal. 



2. Optic. 6. Abducens. 10. Pneumogastric. 



3. Oculo-motor. 7. Facial. n. Spinal- Accessory. 



4. Pathetic. 8. Auditory. 12. Hypoglossal. 



INFLAMMATION OF THE BRAIN TISSUES AND 

 ITS MEMBRANES. 



Bncephalitis. Inflammation of the brain is caused by exposure to 

 extreme heat or cold; excessive continued excitement; direct injuries to 

 the brain; and sometimes appears as a result of influenza, pyaemia, and 

 poisons that directly affect the brain matter. 



Symptoms. Acute inflammation may commence by an increased 

 sensibility to noises, with more or less nervous excitability, contraction 

 of the pupil of the eyes, and a quick hard pulse. These symptoms are 

 not always present in acute attacks. There will follow twitching of the 

 muscles, convulsive or spasmodic movements, eyes wide open with 

 shortness of sight. The animal becomes afraid to have his head handled. 

 Convulsions and delirium will develop, with inability of muscular con- 



