146 PRACTICE OF PHYSIC. 



there are marks of contagion, it may produce a fever of no de- 

 termined period, and an eruption not strictly of a determined 

 kind ; we may perceive, on the contrary, or at least suspect, 

 that the eruption depends on particular circumstances of 

 the fever, and that the fever thus produced by contagion is not 

 always necessarily attended by an eruption. We can apply this 

 to the miliary eruption and several others : but it suffices now 

 to state it generally; we shall consider it more particularly 

 afterwards. This is what we would more properly call a febris 

 cum eocanthemate, the fever accidentally having an eruption 

 as a symptom. 



" There certainly are some species of both these kinds of 

 eruptions, sufficiently well marked ; but there are others in 

 which there is an uncertainty and ambiguity with regard to the 

 order. I have this further observation to make, that those ex- 

 anthemata which are most certainly idiopathic, are most cer- 

 tainly contagious ; and they are contagious with this singular 

 property, that they affect a person but once in the course of his 

 life. I am not to be disturbed with repeated smallpox and 

 measles : for this case is so rare, that we may take the other as 

 the general position. But I am extremely doubtful whether 

 this can be applied as a character of the order. 



" These are some reflections with regard to the establish- 

 ment of this order. With regard to the several genera, a va- 

 riety of circumstances are employed as characters, which it is 

 proper to notice here in a general manner. 



" First, We endeavour to distinguish the several genera of 

 Exanthemata by the species of the fever which belongs to them, 

 excited by the contagion or other causes ; it is sometimes a 

 synocha, sometimes a typhus, and sometimes what is properly 

 called synochus. With regard to several, there is somewhat 

 steady in this matter as a foundation for the character, but I 

 own, that perhaps in no case it is universal, and therefore to 

 be considered as a pathognomonic, essential and inseparable 

 part of the character. For instance, there are certain cases of 

 the plague which are attended by a synochus, and what may 

 almost be termed a synocha ; there are, on the other hand, . 

 cases of smallpox and measles attended by typhus. We give 

 what is most general, nothing is universal ; and therefore take 



