PHYSIOLOGY. 135 



expression " more complete :" it implies that the state of death, 

 the entire, perfect, and complete collapse, is but a lesser degree 

 of excitement ; whereas this must be considered as different from 

 any degree of excitement whatever." 



C XXX VI. From what is now said of the excitement and 

 collapse of the brain, it will appear that we suppose LIFE, so far 

 as it is corporeal, to consist in the excitement of the nervous 

 system, and especially of the brain, which unites the different 

 parts, and forms them into a whole. But, as certain other func- 

 tions of the body are necessary to the support of this excitement, 

 we thence learn, that the causes of death may be of two kinds ; 

 one that acts directly on the nervous system, destroying its ex- 

 citement ; and another that indirectly produces the same effect, 

 by destroying the organs and functions necessary to its support. 

 " I have taken pains to prove (VI. 7-) that though the ac- 

 tion of the brain is the proper vital function, it requires the ex- 

 ternal support of a certain degree of heat, and of the circulation 

 of the blood perhaps as one means of supporting the heat of 

 the system ; and also, that a certain degree of tension in the vessels 

 of the brain, by means of the blood supplied by the action of the 

 heart, is necessary to the energy of the brain. These are the causes 

 which have been commonly attended to. In the system of Boer- 

 haave, for instance, the circulation of the blood and respiration 

 are the primary and fundamental functions ; and where he has at- 

 tempted to account for the causes of death in fevers and in wounds, 

 he looks for those which interrupt the circulation of the blood in 

 the brain. But many of the causes of death do not disturb the cir- 

 culation, except in so far as they take away the excitement, and 

 destroy the moveable nature of the nervous power. In Pathology, 

 and in the prognosis of particular diseases, it is absolutely neces- 

 sary to enter into the distinction of these causes. I call the one di- 

 rect causes, those which act upon the nervous system directly ; 

 the other indirect causes, those which produce the same effect, 

 but by destroying those organs which are necessary to the sup- 

 port of the excitement, viz. the whole system of circula- 

 tion. These indirect causes have been explained in every 

 system ; but I think it necessary to point out the first 

 class the direct causes." Of the first kind are chiefly the 

 causes of sleep operating in a higher degree, as cold, sedative 



