FEVEIIS. 537 



the paroxysms return always upon that day they would have 

 kept to, if they had continued without any interruption, so that 

 the tendency has still continued in the constitution ; and Celsus 

 gives it as a general caution to mark the days in which the In- 

 termittent should return, and then to be cautious with respect to 

 trespasses in the non-naturals. This is a certain proof that 

 a disposition, a tendency, or certain motions analogous to the 

 paroxysms, still lurk in the constitution. 



" The Erratica quintana, coming on the Friday after the Mon- 

 day, is only a tertian which has missed a fit on Wednesday. 

 I will not be positive that it is always so, but there are instances 

 of this kind, where obscure paroxysms have been observed on 

 the Wednesday, which seems to favour this opinion. There are 

 I confess cases that are not to be explained in this way, but they 

 are supposed to belong to the quartan ; and as we cannot cer- 

 tainly assign the reason why the quartan interval is in three 

 days, the same power that protracts the tertian to the quartan, 

 may protract the quartan to the quintan period. 



" The Erratica septana may be explained in a double way, as 

 the septan period belongs to both the tertian and quartan. 

 For the tertian from the Monday returns upon the Sunday, 

 the seventh day, and the quartan form from the Monday re- 

 turns upon the Thursday, or, passing that, upon the Sunday ; so 

 it may be either a period of the tertian missing two fits, or of a 

 quartan missing only one fit. Accordingly, there are frequent 

 instances of both ; and, according to the nature of the fever 

 which subsisted before, we shall be able to determine whether a 

 fever belongs to the tertian or quartan, and explain the septana 

 in one way or other. 



" Vogel is the only person who has given us an Erratica sextana. 

 Were this fact proved, I must confess it would disturb our 

 whole doctrine. I never have any reserve upon that account ; 

 nature in her variety may play us tricks which we may not be 

 able to account for ; but this disturbs our theory very little when 

 neither Sauvages nor I myself could find any instances of it 

 in the history of physic. 



" But there is another form which tends to disturb our theory, 

 where the fit returns every eighth day, of which we have many in- 

 stances. There is nothing, however, in which we are more liable 



VOL. i. - 2 Q. 



