DISEASES OF THE HORSE. 197 



If the disease becomes chronic (encephalitis or meningitis) we must 

 place our reliance upon alteratives and tonics, with such incidental 

 treatment as special symptoms may demand. Iodide of potassium in 

 2-dram doses should be given three times a day, and 1 dram of calo- 

 mel once a day, to induce absorption of effusions or thickened mem- 

 branes. Tonics, in the form of iodide of iron in 1-dram doses, to 

 which is added 2 drams of powdered hydrastis, may also be given 

 every six or eight hours, as soon as the active fever has abated. 

 After the disappearance of the acute symptoms, blisters (cantharides 

 ointment) ma}^ be applied behind the poll. When paralytic effects 

 remain after the disappearance of all other s3"mptoius, sulphate of 

 strychnia in 2-grain doses, in combination with the other tonics, may 

 be given twice a day, and be continued until it produces muscular 

 twitching. In some cases of paralysis, as of the lips or throat, bene- 

 fit may be derived from the moderate use of the electric battery. 

 Many of the recoveries will, however, under the most active and early 

 treatment, be but partial, and in all cases the animals become predis- 

 posed to subsequent attacks. A long period of time should be allowed 

 to pass before the animal is exposed to severe work or great heat. 

 When the disease depends upon mechanical injuries they have to be 

 treated and all causes of irritation to the brain removed. If it is due 

 to stable miasma, uremic poisoning, pyemia, influenza, rheumatism, 

 toxic agents, etc., they should receive prompt attention for their 

 removal or mitigation. 



Cerebral softening, abscess, and sclerosis are practically inacces- 

 sible to treatment, otherwise than such relief as may be afforded by 

 the administration of opiates and general tonics, and, in fact, the diag- 

 nosis is largely presumptive. 



CONGESTION OF THE BRAIN, OR MEGRIMS. 



Congestion of the brain consists in an accumulation of blood in the 

 vessels, also called hyperemia, or engorgement. It may be active or 

 passive — active when there is an undue determination of blood or 

 diminished arterial resistance, and passive when it accumulates in the 

 vessels of the brain, owing to some obstacle to its return by the veins. 



Causes. — Active cerebral congestion may be due to hypertrophy of 

 the left ventrrcle of the heart, excessive exertion, the influence of 

 extreme heat, sudden and great excitement, artificial stimulants, etc. 

 Passive congestion may be produced by any mechanical obstruction 

 which prevents the proper return of blood through the veins to the 

 heart, such as a small or ill-fitting collar, which often impedes the 

 blood current, tumors or abscesses pressing on the vein in its course, 

 and organic lesions of the heart with regurgitation. 



Extremel}" fat animals with short thick necks are peculiarly subject 

 to attacks of cerebral congestion. Simple congestion, however, is 



