382 HORSE, SWINE AND POULTRY DISEASES 



acute inflammation, except as a secondary result. The pia mater 

 is most commonly the seat of inflammation, acute and subacute, 

 but from its intimate relation with the surface of the brain the latter 

 very soon becomes involved in the morbid changes. Practically, 

 we can not separate inflammation of the pia mater from that of the 

 brain proper. Inflammation may, however, exist in the center of 

 the great nerve masses the cerebrum, cerebellum, pons Varolii, or 

 medulla at the base of the brain without involving the surface. 

 When, therefore, inflammation invades the brain and its envelop- 

 ing membranes it is properly called encephalitis; when the mem- 

 branes alone are affected, it is called meningitis; or the brain 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 OP 

 THE BRAIN AND ITS 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 as concussion, or from fracture of the cranium, overexertion, 

 sometimes as sequelae to influenza, poisons having a direct influence 

 upon the encephalic mass, extension of inflammation from neigh- 

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



Symptoms. The diseases here grouped together are accom- 

 panied by a variety of symptoms almost none of which, however, 

 are associated so definitely with a special pathological process as 

 to point unmistakably to a given lesion. Usually the first symp- 

 toms indicate mental excitement, and these are followed by symp- 

 toms indicating depression. Acute encephalitis may be ushered in 

 by an increased sensibility to noises, wdth more or less nervous ex- 

 citability, 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 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 control, or stupor and coma may supervene. Where the 

 membranes are greatly implicated, convulsions and delirium with 

 violence may be expected, but where the brain substances are prin- 

 cipally 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 symptoms may follow one 

 another in rapid succession, and the disease approach a fatal ter- 

 mination in less than twelve hours. In subacute attacks the symp- 

 toms 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 disease, with a tendency to increase until 



