FEVERS. 487 



same series of phenomena again arises, and observes the same 

 course as before; and these states of FEVER and APYREXIA 

 often continue to alternate with one another for many times. In 

 such cases, the length of time from the end of one paroxysm to 

 the beginning of another, is called an INTERMISSION ; and the 

 length of time from the beginning of one paroxysm to the be- 

 ginning of another next succeeding, is called an INTERVAL. 



XXV. When the disease consists of a number of paroxysms, 

 it is generally to be observed that the intervals between them are 

 nearly equal ; but these intervals are of different lengths in dif- 

 ferent cases. The most usual interval is that of forty-eight 

 hours, which is named the TERTIAN period. The next most 

 common is that of seventy-two hours, and is named the QUAR- 

 TAN period. Some other intervals also are observed, particular- 

 ly one of twenty-four hours, named therefore the QUOTIDIAN ; 

 and the appearance of this is pretty frequent. But all other 

 intervals longer than that of the quartan are extremely rare, 

 and probably are only irregularities of the tertian or quar- 

 tan periods. " With respect to these intervals, or periods, 

 it often happens that they continue exactly the same ; but this 

 is not universally the case ; nay, on the contrary, it is perhaps 

 more common for the interval to be a little more or a little 

 less than the time mentioned, which has given occasion to the 

 terms postponing and anticipating paroxysms. This, how- 

 ever, when duly considered, will be found not to disturb our 

 general position, that the tendency of nature is to form intervals 

 of 48, 72, or 24 hours. 11 



XXVI. The paroxysms of pure intermittent fevers are always 

 finished in less than twenty-four hours ; and though it happens 

 that there are fevers which consist of repeated paroxysms, 

 without any entire intermission between them, yet in such 

 cases it is observed, that though the hot and sweating stages of 

 the paroxysm do not entirely cease before the twenty-four hours 

 from their beginning have expired, they suffer, however, before 

 that time, a considerable abatement or REMISSION of their 

 violence ; and, at the return of the quotidian period, a pa- 

 roxysm is in some shape renewed, which runs the same course 

 as before. This constitutes what is called a REMITTENT FEVER. 



XXVII. When in the remittents the remission is considerable, 



