342 DISEASES AFFECTING THE CEREBRAL CIRCULATION. 



afforded by the collar being displaced forward, when the 

 excitation steadily subsides and the animal proceeds to his 

 work. When, however, the symptoms increase in severity, 

 the muscular tremors are more extensive, excitement is greater, 

 and the fury becomes uncontrollable ; the animal plunging for- 

 ward or rearing, falls prostrate on the ground. When down, 

 the paroxysm rarely lasts long, the cause being removed during 

 the struggling by the displacement of the collar and the 

 establishment of a free return of blood from the brain. 



Treatment. — In the management of cases of megrims the 

 natural indications are, first, to remove the pressure from the 

 jugulars by pushing the collar forward and thereby permit- 

 ting a free return of the blood from the cranium; second, to 

 allay the cerebral excitement and restore the natural tone and 

 calibre of the vessels by dashing cold water over the head and 

 face. Those cases which are complicated with gastric and 

 other disturbances must have these functional conditions 

 specially attended to. While, should the formation of the 

 neck or manner of working be such as to render recurrence 

 troublesome, the ordinary neck-collar must be dispensed with, 

 and a breast-strap used instead. 



II. Cerebral An.emia. 



That this and other disorders of the cerebral circulation 

 mentioned occur in the horse there is little doubt ; it may be 

 less frequently than in man, but still more so than in other of 

 our patients. 



Causation. — Anaemia of the brain-structure may be noticed 

 both as a general diseased condition and as affecting portions 

 or limited areas of the cerebral structure. In the former deve- 

 lopment it is usually in conjunction with conditions the oppo- 

 site of those mentioned as connected with hyperemia. 1. In 

 states of general anremia; 2. With enfeebled cardiac power 

 and action ; 3. With extensive local interference with blood- 

 supply, the result of intercranial lia3mal obstruction. 



Anatomical Characters. — There is unnatural pallor, both of 

 membranes and brain-substance. The latter is also often damp 

 and oedematous ; and on making a section of it the free surface 

 is marked with fewer and smaller blood-spots than in a natural 

 condition. In many instances, particularly of local anaimia. 



