DISEASES OF THE NERVOUS SYSTEM. 213 



the seat <»f iiifliiimiiatioii. aciiti' and sul>ac-iit«', but from its intimate 

 relation with the siiiface of the l»rain the hitter very soon becomes 

 involved in the morbid changes. Practically, we can not separate 

 inflammation of the pia mater from that of the brain ])roper. Inflam- 

 mation may. howe\ er. exist in the center of the great nerve ma.s.scs — • 

 the cerebrum, cerebellum, pons Varolii, or medulla at the base of the 

 brain — without invoh ing the surface. AMien. therefore, inflamma- 

 tion invades the brain and its enveloping membranes it is piopeily 

 called encephalitis; when the membranes ahme are affected it is 

 called meningitis, or the brain substance alone cerebritis. Since all 

 the conditions merge into one another and can scarcely be recognized 

 separately during the life of the animal, they may here be considered 

 t(;gether. 



f'ausfs. — Kxi)o>ure to extreme heat or cold, sudden and extreme 

 changes of temperature, excessive continued cerebral excitement, too 

 much nitrogenous feed, direct injuries to the brain, such as concus- 

 sion, or from fracture of the cranium, overexertion, sometimes as 

 sequela^ to influenza, pyemia, poisons having a direct influence uj)on 

 the encephalic mass, extension of inflammation from neighboring 

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



Syjnptomf(. — The diseases here grouped together are accompanied 

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

 ciated so definitely with a special jiathological process as to point 

 unmistakably to a given lesion. Usually the first symptoms indicate 

 mental excitement, and are followed by symptoms indicating depres- 

 si(m. Acute encephalitis may be ushered in by an increased sensi- 

 bility to noises, with more or less nervous excitability, contraction of 

 the pupils of the eyes, and a quick, hard pulse. In Aery acute at- 

 tacks these symptoms, however, are not always noted. This condi- 

 tion 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. AVhen the membranes are greatly impli- 

 cated, convulsions and delirium w ith violence nuiy be expected, but if 

 the brain sub>tances aie principally affected stu|)or and coma will ])e 

 the prominent symptoms. In the former condition the pulse will be 

 •juick and hard: in the latter, soft and depressed, with often a dilata- 

 tion of the pujnls, and deep, slow, stertorous breathing. The symj)- 

 toms may follow one another in rapid succession, and the disease 

 approach a fatal termination within 1'2 hom-s. In subacute at- 

 tacks the symptoms are better defined, and the animal seldom dies 

 before the third day. Within three or four days gradual improve- 

 ment may become manifest, or cerebral softening with partial paral- 



