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recourfe to the effervefcence of the blood, 
which, in his opinion, only could be ef¬ 
fected in a certain fpace of time. 
It is not to the fluids that the exigence 
of this phenomenon is to be attributed, 
but to the very nature of the nervous fyf» 
tem. If we pay attention to the affedions 
of this fyftem, we lhall find that they 
obferve almoft always an order and re¬ 
gularity in their periods, and we lhall 
likewife fee that many of the operations in 
the healthy animal obferve the fame laws. 
A lingular obfervation is made by Syden¬ 
ham, which is not at all favourable to his 
theory, viz.—That the ufe of clyfiers and 
cathartics in the decline of continued fe¬ 
ver, has fometimes relieved the patient, and 
produced a complete apyrexia, but that in a 
day or two the fever has recurred with the 
fame fet of fymptoms, attending its firll 
attack, and its progrefs and duration were 
the fame with the firll. “ Mud porro obfer- 
vatu 
