121 



of diseases. In most cases the most skilful phy. 

 sieians acknowledge they have nothing but conjec- 

 tures to offer. We may give a specimen with re- 

 gard to fevers, the most common of all distempers. 

 These are of various kinds : at present we will speak 

 of intermitting fevers only. Most of these agree in 

 the following symptoms. During the approach of 

 the fit, cold and shivering seize the body, with a 

 small and slow pulse. Heat succeeds, with a quick, 

 strong, hard pulse, followed by sweat and a softer 

 pulse. These fits return at stated times. 



It is supposed, that these changes in the blood 

 arise from some foreign matter mixed with it, which it 

 cannot readily assimilate, and which therefore must' 

 in some measure hinder its motion: perhaps because the 

 particles of it are too large, too long, or branching out. 

 When the circulation is hindered or retarded, chilness 

 naturally follows. And if these particles, sticking in 

 the finer passages are pressed on by the affluent blood, 

 this will occasion both a shock and tremor of the 

 muscles, and make the pulse more weak and slow. 

 But when they are at length broken and comminuted 

 by the continued afflux of the blood, it will flow 

 more violently, and of course occasion heat> which, 

 driving the blood to the surface of the body, many 

 of its thinner particles will burst through the pores, 

 in the form of sweat. As to the fevers returning at 

 stated times, it is supposed, the peccant matter is ge. 

 nerated from time to time, and mingled with the 

 blood afresh, whence the same symptoms of course 

 return, and that with more or less violence, as more 

 or less of that matter is generated. And as this is 

 done more swiftly or slowly, the fever returns in one, 

 two, or three days. But all this is mere conjecture. 

 It may be so : and it may not. So that though we 

 may guess much, we know nothing about it. 



8. It is sufficient for us to know how we may avoid 

 diseases, whether we can account for them or not. 

 To this end, we should avoid whatever in meat, drink, 



TOL. I. G 



