Sip. I. 5. 2. THEORY OF FEVEU. 455 



Tract on Simple Fever, page 168. He asserts, that those people 

 who have been confined some time in a very warm atmosphere, 

 as of 120 or 130 degrees of heat, do not feel cold, nor are sub- 

 ject to paleness of their skins, on coming into a temperature of 

 30 or 40 degrees; which would produce great paleness and pain- 

 ful sensation of coldness in those, who had been some time con- 

 fined in an atmosphere of only 86 or 90 degrees. Analogous to 

 this, an observing friend of mine assured me, that once having 

 sat up to a very late hour with three or four very ingenious and 

 humorous companions, and drunk a considerable quantity of 

 wine; both contrary to his usual habits of life; and being ob- 

 liged to rise early, and to ride a long journey on the next day, 

 he expected to have found himself weak and soon fatigued; but 

 on the contrary he performed his journey with unusual ease and 

 alacrity; and frequently laughed, as he rode, at the wit of the 

 preceding evening. In both these cases a degree of pain or 

 pleasure actuated the system; and thus a sensorial power, that 

 of sensation, was superadded to that of irritation, or volition. 

 See Sect. XXXIV. 2. 6. 



2. Similar to this, when the energetic exertions of some parts 

 of the system in the hot fit of fever arise to a certain excess, a 

 degree of sensation is produced; as of heat which particularly 

 increases the actions of the cutaneous vessels, which are more 

 liable to be excited by this stimulus. When this additional sen- 

 sorial power of sensation exists to a greater degree, the pulse, 

 which was before full, now becomes hard, owing to the inflam- 

 mation of the vasa vasorurn, or coats of the arteries. In these 

 cases whether there is any topical inflammation or not, the fever 

 ceases to intermit; but nevertheless there are daily remissions 

 and exacerbations of it; which recur for the most part about six 

 in the evening, when the solar gravitation is the least, as men- 

 tioned in Sect. XXXVI. 3. 7. 



3. Thus the introduction of another sensorial power, that of 

 sensation, converts an intermittent fever into a continued one. If 

 it be attended with strong pulse, it is termed febris sensitiva irri- 

 tata, or pyrexia, or inflammation; if with a weak pulse, it is term- 

 ed febris sensitiva inirritata, or typhus gravior, or malignant 

 fever. The seat of the inflammation is in the glandular or capil- 

 lary system, as it consists in the secretion of new fluids, or new 

 fibres, which form new vessels, as they harden, like the silk of 

 the silk- worm. See Art. 15. of this Supplement. 



VI, Circles of Irritative Associate Motions. 

 1. There are some associate motions, which are perpetually 



