MEGRIMS. 339 



supply of blood, or tlie opposite, in the vessels of the brain — 

 cerebral congestion and anaemia ; 2. Cerebral thrombosis and 

 embolism ; 3. Cerebral haemorrhage. 



Without entering into the consideration of conditions, both 

 admitted and disputed, in connection with the cerebral circula- 

 tion, it will be well to recollect, as enabling us to understand 

 many morbid phenomena, that one peculiarity is the absence 

 in the true cerebral circulation of free anastomosis, save of a 

 capillary nature. In this way we account for, and can better 

 understand, the largely distributed but limited areas of struc- 

 tural change which occur in the brain substance from plug- 

 ging of minute vessels, or from escape of their contents. 



I. Cerebral Congestion — Megrims — Vertigo— Staggers. 



Pathology, a. Nature of the Affection. — These different 

 terms, and probably some others, have all been applied to that 

 condition, which is certainly the most frequently occurring, of 

 the purely cerebral diseases of the horse. It is not, however, 

 perfectly clear that these different names have always been 

 employed to indicate precisely the same affection, or that each 

 of them is looked upon by all as indicating the same morbid 

 action. The terms vertigo and staggers, particularly the latter, 

 have probably been more frequently used to indicate the exist- 

 ence of those symptoms merely — without reference to the condi- 

 tions to which such symptoms point, or from which they arise 

 — associated with any cerebral disturbance exhibiting obtuse- 

 ness of perception, and a deficiency of control over the voluntary 

 movements of the limbs. In this way have those truly gastric 

 disturbances, which by sympathy or reflected action induce dis- 

 ordered cerebral function, come to be grouped and spoken of 

 along with the more purely cerebral diseases. 



By the term megrims, or cerebral congestion, we would desire 

 to indicate that particular cerebral disturbance in the horse, 

 usually sudden in its onset, and of very temporary duration, 

 but liable to recurrence, marked by much excitement, per- 

 version or impairment, not merely of perception and special 

 sensation, but also to some extent of common sensation and 

 voluntary motion ; these vertiginous symptoms occurring, in 

 the greater number of cases, where the animals are actually 

 engaged in draught, working in the ordinary neck-collar. 



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