DISEASES OF THE HORSE. 19& 



pia mater from that of the brain proper. Inflammation may, however, 

 exist in the center of the great nerve masses — the cerebrum, cerebel- 

 lum, pons Varolii, or medulla at the base of the brain — without involv- 

 ing- the surface. When, therefore, inflammation invades the brain and 

 its enveloping membranes it is propeVly called encepJialitis ; when the 

 membranes alone are affected, it is called meningitis; or the bi'ain sub- 

 stance alone, cerebritis. Since all of the conditions merge into each 

 other and can scarcely be recognized separately during the life of the 

 animal, they may here be considered together. 



encephalitis, meningitis, and cerebritis (inflammation of the brain and it8. 

 membranes). 



Causes.- — Exposure to extreme heat or cold, sudden and extreme 

 changes of temperature, excessive continued cerebral excitement, over- 

 feeding with nitrogenous foods, direct injuries to the brain, such a» 

 concussion, or from fracture of the cranium, overexertion, sometimes- 

 as sequelae to influenza, pyemia, poisons having a direct influence upon 

 the encephalic mass, extension of inflammation from neighboring^ 

 structures, food poisoning, tumors, parasites, metastatic abscesses, etc.. 



Sy7n/ptoms. — The diseases here grouped together are accompanied 

 by a variety of symptoms almost none of which, however, are asso- 

 ciated so definitely with a special pathological process as to point unmis- 

 takably to a given lesion. Usually the first s^miptoms indicate mental 

 excitement and these are followed by symptoms indicating depression.. 

 Acute encephalitis may be ushered in by an increased sensibility to- 

 noises, with more or less nervous excitability, contraction of the pupils- 

 of the eyes, and a quick, hard pulse. In very acute attacks these 

 symptoms, however, are not always noted. This condition will soon 

 be followed by muscular twitchings, convulsive or spasmodic move- 

 ments, eyes wide open with shortness of sight. The animal becomes- 

 af raid to have his head handled. Convulsions and delirium will develop^ 

 with inability of muscular control, or stupor and coma ma}^ supervene. 

 Where the membranes are greatly implicated, convulsions and delirium 

 with violence may be expected, but where the brain substances are 

 principally affected stupor and coma will be the prominent symptoms. 

 In the former condition the pulse will be quick and hard; in the latter,, 

 soft or depressed with often a dilatation of the pupils, and deep, slow, 

 stertorous breathing. The sj^mptoms may follow one another in rapid 

 succession, and the disease approach a fatal termination in less thait 

 twelve hours. In subacute attacks the symptoms are better defined, 

 and the animal seldom dies before the third day. Within three or 

 four days gradual improvement may become manifest, or cerebral 

 softening with partial paralysis may occur. In all cases of encephalitis- 

 there is a marked rise in temperature from the very onset of the dis- 

 ease, with a tendency to increase until the most alarming symptoms 

 14384—03 13 



