352 PRACTICE OF PHYSIC. 



MCXLYII. We begin with considering the cases depend- 

 ing upon compression. 



The compression occasioning hemiplegia may be of the same 

 kind, and of all the different kinds that produce apoplexy ; and, 

 therefore, either from tumour, over-distention, or effusion. The 

 existence of tumour giving compression may often be better dis- 

 cerned in the case of palsy than in that of apoplexy, as its effects 

 often appear at first in a very partial affection. 



MCXLVIII. The other modes of compression, that is, of 

 over-distention and effusion, may, and commonly do, take place 

 in hemiplegia ; and, when they do, their operation here differs 

 from that producing apoplexy, by its effects being partial, and 

 on one side of the body only. 



It may seem difficult to conceive that an over-distention can 

 take place in the vessels on one side of the brain only ; but it 

 may be understood : and, in the case of a palsy which is both 

 partial and transitory, it is perhaps the only condition of the 

 vessels of the brain that can be supposed. In a hemiplegia, in- 

 deed, which subsists for any length of time, there is probably 

 always an effusion, either sanguine or serous : but it is likely 

 that even the latter must be supported by a remaining conges- 

 tion in the blood-vessels. 



MCXLIX. That a sanguine effusion can happen without 

 becoming very soon general, and thereby occasioning apoplexy 

 and death, may also seem doubtful. But dissections prove, that 

 in fact, it does happen, occasioning palsy only ; though it is 

 true, that this more commonly depends upon an effusion of ser- 

 ous fluid, and of this only. 



MCL. Can a palsy occasioned by a compression remain, 

 though the compression be removed ? 



" The prognosis of palsy depends on the part affected, viz. the 

 brain, medulla spinalis, or particular nerves: for these are of dif- 

 ferent use in the system, that is more or less universal and ne- 

 cessary. 



" The intellectual powers are particularly connected with the 

 brain, so that this organ is of the greatest importance ; and 

 hence, all palsies that arise from the brain are of greater danger 

 and more difficult cure than those which arise from the medulla 

 spinalis: but palsies arising from the brain are less common 



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