DISEASES OF THE HORSE. 25 



on one side are interfered with, the result is paralysis of one side of 

 the body. 



The small brain, or cerebellum, governs the regularity, or coordi- 

 nation, of movements. Disturbances of the cerebellum cause a totter- 

 ing, uncertain gait. In the medulla oblongata, which lies between the 

 spinal cord and the cerebellum, are the centers governing the circula- 

 tion and breathing. 



The spinal cord carries sensor}^ messages to the brain and motor 

 impressions from the brain. The anterior portions of the cord con- 

 tain the motor paths, and the posterior portions of the cord contain 

 the sensory paths. 



Paralysis of a single member or a single group of muscles is known 

 as monoplegia and results from injury to the motor center or to a 

 nerve trunk leading to the part that is involved. Paral3^sis of one- 

 half of the bod}' is known as hemiplegia and results from destruction 

 or severe disturbances of the cerebral hemisphere of the opposite side 

 of the bod}' or from interference with nerve paths between the cere- 

 bellum, or small brain, and the spinal cord. Paralysis of the poste- 

 rior half of the bod}' is known as paraplegia and results from derange- 

 ment of the spinal cord. If the cord is pressed upon, cut, or injured, 

 messages can not be transmitted beyond that point, and so the poste- 

 rior part becomes paralyzed. This is seen when the back is fractured. 



Abnormal mental excitement may be due to congestion of the brain 

 or to inflammation. The animal so afflicted becomes vicious, pays no 

 attention to commands, cries, runs about in a circle, stamps with the 

 feet, strikes, kicks, etc. This condition is usually followed by a dull, 

 stupid state, in which the animal stands with his head down, dull and 

 irresponsive to external stimuli. Cerebral depression also occurs in 

 the severe febrile infectious diseases, in chronic hydrocephalus, in 

 chronic diseases of the liver, in poisoning with a narcotic substance^ 

 and with chronic catarrh of the stomach and intestines. 



Fainting is a symptom that is not often seen in horses. When it 

 occurs it is shown by unsteadiness of gait, tottering, and, finally, inabil- 

 ity to stand. Th§ cause usually lies in a defect of the small brain, or 

 cerebellum. This defect may be merely in respect of the blood supply, 

 to congestion, or to anemia, and in this case it is likely to pass away and 

 may never return, or it may be due to some permanent cause, as a 

 tumor or an abscess7 or it may result from a hemorrhage, from a defect 

 of the valves of the heart, or from poisoning. 



Loss of consciousness is known as coma. It is caused by hemorrhage 

 in the brain, by profound exhaustion, or may result from a saturation 

 of the system with the poison of some disease. Coma may follow 

 upon cerebral depression, which occurs as a secondary state of inflam- 

 mation of the brain. 



