ERUPTIVE FEVERS. 149 



very numerous upon every other part of the body, extremely 

 rarely appears on the face. 



" All these particulars will be touched again, when we con- 

 sider the particular genera ; but you will find some use from 

 this^general view of them in pointing out a comparison." 



HAP. I. OF THE SMALLPOX. 



DLXXXVII. The smallpox is a disease arising from a con- 

 tagion of a specific nature, which first produces a fever, and, on 

 the third or fourth day thereof, produces an eruption of small 

 red pimples. These are afterwards formed into pustules, con- 

 taining a matter, which, in the course of eight days from the 

 time of the eruption, is changed into pus. After this, the mat- 

 ter dries, and falls off in crusts, 



" I have in my definition said, ' tertio die incipit et quinto 

 diejinitur eruptioS To persons conversant with the writings 

 of Dr. Sydenham, this may appear odd, as Sydenham has said 

 that the eruption appears on the fourth day of the disease, 

 and I have ventured to say, without exception, that it is on the 

 third day. In a thousand instances which I have seen, the 

 eruption has not been entirely delayed to the fourth day. I 

 very lately, in the clinical lectures, treated of a patient in the 

 smallpox, who gave me an opportunity to explain this matter. 

 The eruption did not appear till the fourth day, in the common 

 reckoning of physicians the disease attacked on the 14th day 

 of the month, and the eruption appeared on the 17th : now, 

 if the disease made its attack any time before noon, the 

 reckoning of the physicians would be correct the 17th would 

 be the fourth day; but when it attacks in the afternoon, 

 then, I say, the first day is to be considered as finished only on 

 the evening of the second, and the third day of the disease will 

 extend to the evening of the 17th ; and, as the eruption was 

 perceived on the morning of that day, it was truly only the 

 third day of the disease. It may be further observed, that this 

 is founded upon another consideration, viz. that the motions of 

 the smallpox are periodical and regular, and proceed on the ter- 



