500 PRACTICE OF PHYSIC. 



causes of increased excitement of the brain which will have a 

 similar effect. 



"It belongs to this place to observe, that other symptoms oc- 

 cur in fevers, such as those of sleep and watching, which are to 

 be explained on the same footing. If you consult the writings of 

 Boerhaave, more especially as they are explained by Van Swieten, 

 on Coma and Pervigilium, you will find that these symptoms are 

 explained by the state of the organs of circulation in the brain ; 

 and this may be often the cause, but if the physiology I have 

 delivered with respect to sleep and watching (Physiology, 

 C XX VI I.) be well founded, nothing is more evident than that 

 the Coma may depend upon the affection of the nervous system, 

 and upon this alone independently of the sanguiferous, viz. upon 

 its state of excitement and collapse ; the cause of fever inducing 

 that state in which the coma consists. The deliria being transi- 

 tory, is a strong proof of their depending upon the nervous sys- 

 tem ; for what vanishes in an hour or two cannot depend upon any 

 considerable topical affection, or any considerable derangement of 

 the circulating fluids, but rather must depend upon the dimin- 

 ished excitement of the brain, or on the exercise of its energy. 



" We here also take notice of the horror and tremor which 

 commonly form so considerable a share of the cold fit of fever. 

 These symptoms are upon other occasions the effect of cold ap- 

 plied to the body, and therefore may be considered as the effects 

 of the sense of cold, which always precedes and accompanies 

 the beginning of fever. It will be of use to consider this mat- 

 ner still farther, and to inquire more particularly in what tremor 

 consists. 



" Tremor occurs in a state of debility, and is an effort arising 

 from a constant alternation of the debility and the effort of the 

 will. And here it is to be observed, that there are many in- 

 stances of motions produced by the effort of the energy of the 

 brain, without any consciousness of the concurrence of the will 

 to produce such motion. Thus, the chattering of the teeth, or 

 tremor of the lower jaw, arises from its tendency to fall down in 

 consequence of its weight, and the constant effort of the energy 

 of the brain to raise it. 



" Tremor then occurring in fever is to be considered as a 

 mark of the reaction of the system, not as a part of the direct 



