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cranium. Neither is the arachnoid often affected with acute inflam- 

 mation except as a secondary result. The pia mater is most com- 

 monly the seat of inflammation, acute and subacute, but from its 

 intimate relation with the surface of tlie bi-ain the latter very soon 

 becomes involved in the morbid changes. Practicallj', 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 A^arolii, or medulla at the 

 base of the brain, without involving the surface. AYhen, therefore, 

 inflammation invades the brain and its enveloping membranes it is 

 properlj^ called enceplialUisj when the membranes alone are affected 

 it is called meningitis; or the brain substance alone, cerebritis. 



ENCEPHALITIS — INPLAMMATIOX OF THE BRAIN AND ITS MEMBRANES. 



Causes. — Exposure to extreme heat and cold, excessive continued 

 cerebral excitement, direct injuries to the brain, such as concussion, 

 or from fracture of the cranium, sometimes as a sequela to influ- 

 enza, pj^seniia, poisons having a direct influence ni^on the encephalic 

 mass, etc. 



Sijinptoms. — Acute encephalitis may be ushered in by an increased 

 sensibility to noises, with more or less nervous excitability, contrac- 

 tion 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 v,'itli shortness of sight. 

 The animal becomes afraid to have his head handled. Convulsions 

 and delirium may 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 principally affected stupor and 

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

 pulse Avill 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 termination in less than twelve hours. In 

 subacute attacks the sj^mptoms are better defined, and the animal 

 seldom dies before the third daj^ Within three or four days gnulual 

 imjirovement may become manifest, or cerebral softening Avith par- 

 tial 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 the most alarming symptoms develop, 

 succeeded by a decrease when coma becomes manifested. The vio- 

 lence and character of the symptoms greatly depend upon the extent 

 and location of the structures involved. Thus, in some cases we may 

 find marked paralysis of certain muscles, while in others we nmy have 

 spasmodic rigidity of muscles in a certain region. Very rarely the 



