DISEASES OF THE NERVOUS .SYSTEM. 101 



The brain is contained within the cavity of the skUlI and is con- 

 tinuous with the spinal cord; there is nothing to mark the place 

 where one leaves off and the other begins. The brain is the seat of 

 reason and intelligence. Voluntary effort originates from the brain. 

 Coordination, or harmony of movement, is controlled by the rear 

 portion of the brain, known as the cerebellum. 



The meninges are the membranes, three in number, which envelop 

 the brain and spinal cord, and separate them from the bones which 

 form the walls of the cranial cavity and spinal canal. 



The sympathetic, also called the ganglionic, division of the nervous 

 system consists of two chains of ganglia, reaching from the head to 

 the tail, situated beneath the spinal column, one on either side. The 

 presence of the ganglia or enlargements on the cords give them their 

 chainlike appearance. 



The sympathetic nerves are closely connected with the cerebro- 

 spinal nerves, but are not under the control of the will. 



INFLAMMATION OF THE BRAIN AND ITS MEMBRANES (STAGGERS). 



Inflammation of the brain is technically termed encephalitis and 

 of its membranes cerebral-meningitis, but as both conditions usually 

 occur together, and since it is practically impossible to distinguish 

 one from the other by the symptoms shown by the diseased animal, 

 they may as well be considered together here as varieties of the same 

 disease. Staggers, coma, frenzy, etc., are terms that are sometimes 

 applied to this disease in its different forms or stages. 



Causes. — Severe blows on the head with a hard object, or the head 

 coming violently in contact with the ground or other hard substance 

 in a fall, may be followed by encephalitis. Irritation caused by 

 tumors in the brain may produce inflammation. Feed containing 

 deleterious matters — for example, ergot (see PL V) and other fungi 

 which contain a narcotic principle — is the most frequent cause of this 

 affection, and hence it is often called " grass staggers " and " stomach 

 staggers." Highly nitrogenous feeds are blamed for causing this dis- 

 ease. Parasites, mineral and narcotic poisons, hot weather, and 

 severe exertion or excessive excitement may cause this condition. 

 Inflammation of the brain may occur as a complication of some infec- 

 tious disease or may follow some forms of indigestion. In many 

 localities certain plants have the reputation of causing staggers. 



Symptoms. — The sj^mptoms vary much, but a careful observer will 

 detect a trouble connected with the nervous system without much 

 uncertainty. The first signs may be those of frenzy, but generally 

 at the start the animal is dull and sleepy, with little or no inclination 

 to move about; the head may be pressed against the wall or fence 

 and the legs kept moving, as if the animal were endeavoring to walk 

 through the obstruction; the body, especially the hind part, may be 



