502 PRACTICE OF PHYSIC. 



heart and larger arteries is increased (XL.), and continues so 

 (XLI.) till it has had the effect of restoring the energy of the 

 brain, of extending this energy to the extreme vessels, of restor- 

 ing therefore their action, and thereby especially overcoming 

 the spasm affecting them ; upon the removing of which, the 

 execretion of sweat, and other marks of the relaxation of excre- 

 tories take place. 



" Now this is what I call the theory of fever; but take notice 

 what kind of a theory it is ; for it is no more than saying that 

 there are certain states of the body which are combined together 

 in a certain order Vf succession, and that from this constant 

 combination they are to be considered as a series of causes and 

 effects. This I assume as a fact, and I suppose that this con- 

 nexion is determined by a certain mechanism of the body ; but 

 I do not explain the nature of this ; I might offer conjectures 

 upon the subject, but while they are only conjectures, I shall 

 not trouble you with them, so shall go no further." 



XL VI I. This doctrine will, as I suppose, serve to explain 

 not only the nature of fever in general, but also the various 

 cases of it which occur. Before proceeding, however, to this, 

 it may be proper to point out the opinions, and, as I appre- 

 hend, the mistakes, which have formerly prevailed on this 

 subject. 



XL VIII. It has been supposed, that a lentor or viscidity 

 prevailing in the mass of blood, and stagnating in the extreme 

 vessels, is the cause of the cold stage of fevers and its conse- 

 quences. But there is no evidence of any such viscidity previ- 

 ously subsisting in the fluids ; and, as it is very improbable that 

 such a state of them can be very quickly produced, so the sud- 

 denness with which paroxysms come on, renders it more likely 

 that the phenomena depend upon some cause acting upon the 

 nervous system, or the primary moving powers of the animal 

 economy. (See Van Swieten apud Boerh. Aph. 755.) 



XLIX. Another opinion, which has been almost universally 

 received, is, that a noxious matter introduced into, or generated 

 in the body, is the proximate cause of fever; and that the in- 

 creased action of the heart and arteries, which forms so great a 

 part of the disease, is an effort of the vis medicatrix naturae 

 to expel this morbid matter; and particularly to change or 



