FEVERS. 581 



es to it, as Vertigo and Tinnitus aurium. I need not re- 

 peat what is to be said in theory upon this subject; the 

 action of the heart depends upon the constant energy of the 

 brain, and the energy of the brain itself upon the action of the 

 heart, or the impulse of the blood in its vessels. (See Physi- 

 ology, C XXXIV.) It is a sign, therefore, that the heart is 

 weak, when it is not able to propel the blood into the vessels 

 of the head in an erect posture ; and the brain also is thereby 

 considerably weakened, the influence of these organs being mu- 

 tual and reciprocal. But however you consider this matter, in 

 every light these symptoms are expressions of considerable de- 

 bility. As they however do not always occur, we generally judge 

 of the force of the circulation by the state of the pulse; we sup- 

 pose debility, where the pulse is weak, and, by a necessary con- 

 sequence, frequent, and also in the same case unavoidably irre- 

 gular. If the action of the heart is weak, the quantity of blood 

 in the ventricles is not entirely evacuated, so that they are 

 sooner filled and irritated to a new contraction. Perhaps there 

 is a sense in us, though little perceived by the mind, that in 

 consequence of any difficulty being presented, some degree of 

 reaction arises, or some effort to exert the force of the circulation ; 

 and this will always account for the frequency of the pulse. 

 In consequence of the weakness every muscular fibre is liable 

 to be unsteady, and the heart itself is liable to tremor as any 

 other muscle is ; when weak, therefore, it will likewise show an 

 irregularity or inequality in the repetition of the pulse. 



" When upon this subject, it is necessary to take notice of a 

 slow pulse occurring in fevers. A frequent pulse is the very 

 characteristic of fevers, but we know that we must not depend 

 upon that single circumstance alone, and, accordingly, at present 

 most physicians agree that there is a nervous fever where there 

 is a pulse ( sanorum similis, 1 nay, where it is even slower than is 

 usual in a state of health. I cannot refuse that the fact occurs, 

 but I must say that I have not met with this circumstance in 

 one out of an hundred of the nervous fevers that I have had oc- 

 casion to observe. I have, however, in complaisance to the fact 

 set down in the character of the typhus, ' pulsus plerumque fre- 

 quens,' but I would say, that in general, nay, very universally, the 

 pulse is, on the contrary, more frequent in nervous fevers than 



