FEVERS. 509 



this depends upon the original conformation of the body, or 

 upon certain powers constantly applied to it, and inducing a 

 habit, I cannot positively determine : but the returns of sleep 

 and watching, of appetites and excretions, and the changes 

 which regularly occur in the state of the pulse, shew sufficient- 

 ly that in the human body a diurnal revolution takes place. 



" The course, I say, of every intermittent fever which I 

 know, consists of repeated paroxysms, with a distinct apyrexia, 

 and is always finished in less than twenty-four hours, whether the 

 fever be quotidian, tertian, or quartan ; and there is not one ob- 

 servation in physic in contradiction to this. The same applies 

 to every fever which physicians have been pleased to call Remit- 

 tent ; and it also holds with regard to those which are called 

 Continued, in which the alternate states are the least distinctly 

 observed; but if they can be observed at all, they are found to 

 occur once in the twenty-four hours. 



" I do not pretend to know so much of the nature of fevers or 

 of the operation of those causes which determine the paroxysm 

 to run such a course, as to be able sufficiently to clear up this 

 matter ; but I presume, that this phenomenon of the paroxysm 

 of fever being always finished in less than twenty-four hours, 

 does not depend on the cause of the fever, but rather on the 

 nature of the economy itself, or upon some law of the system 

 determining it to a diurnal revolution which modifies fevers in 

 this respect. It may proceed from those causes which are pro- 

 duced by the diurnal revolution of the earth, viz. the regular 

 alternation of heat and cold, light and darkness, which must 

 greatly influence our constitution. We know, indeed, that the 

 mere alternation of light and darkness alters the routine of all 

 common business, and influences the whole train of our affairs ; 

 and from this we can see sufficient cause for establishing such a 

 law, or for disposing a system so readily used to habit as ours 

 is, to diurnal revolutions. It must be allowed, however, that 

 this is still but reasoning ; I would add, therefore, that, what- 

 ever the cause may be, I presume from facts, that in the hu- 

 man system, whether from its original constitution or from the 

 cause just mentioned, a diurnal revolution takes place. The 

 phenomena of sleep and watching, the return of hunger, and 

 of the excretions, which all recur in the space of twenty-four 



