136 PHYSIOLOGY. 



passions, poisons, and all causes of very violent excitement.- 

 u With regard to cold, I have sufficiently explained myself 

 (CXXVIII.), proving that it acts upon the nervous system, 

 inducing sleep and even death, and that the stagnation of the 

 fluids, and cessation of the action of the heart, are merely a 

 consequence of its action upon the nervous system. Of the 

 sedative passions, fear may be considered as one, which, when 

 it produces death, acts first upon the nervous system, and only 

 secondarily upon the heart and its dependencies. With re- 

 gard to poisons, I have not placed the narcotics here; but 

 whether these have that power or not, there are many poi- 

 sons which, from the whole phenomena of their operations, 

 undoubtedly act directly upon the nervous system. I add 

 another particular, which is not so obvious, viz. all causes 

 of very violent excitement.'' Excitement is necessarily alter- 

 nated with a corresponding degree of collapse (CXXX.), 

 and the exercise of the animal powers necessarily induces the al- 

 ternate state of rest, as in sleep. This I illustrate here by two 

 causes of death : electricity and a sudden transport of joy. The 

 first operation of electricity is upon the nervous system ; its ef- 

 fects in stupifying and killing animals are in proportion to its 

 being directed more immediately to the brain. The manner of 

 its operation has been disputed. It has been supposed that the 

 violence of the stroke breaks the tender structure of the brain ; 

 and I allow that this may be sometimes the case, and there may 

 even be marks of effused blood ; but Dr. Priestley, who has par- 

 ticularly considered this subject, maintains, as the result of all 

 his observations, that electricity kills without any evident ten- 

 sion or violence done to the organ of the brain. In the case of 

 a sudden transport of joy, (see Medical Commentaries, vol. vi. 

 p. 256.) no body can doubt that the operation is entirely upon 

 the nervous power, upon the organ of the soul and of our emotions 

 and our passions ; and we must admit that merely by the force 

 of violent excitement an entire and perfect collapse takes place, 

 and therefore death is produced.' 1 



CXXX VI I. This subject may receive still further illustra- 

 tion from considering the state of the other parts of the nerv- 

 ous system with respect to excitement and collapse. In the 

 nerves strictly so called (XXIX. 2.), we do not know that the 



