SEC. VI.] INFLUENCE OF NERVES ON ANIMAL HEAT. 421 



passion, and consequently that there is no function of the 

 human economy, which can easily resist so great an evil." 

 It seems, indeed, possible, that the nerves, when irritated by 

 anger, may, in virtue of their influence on the secreting 

 viscera, render the secretions irregular, disordered, and impure, 

 although we cannot determine in what that impurity may 

 consist, which is added to the secretions by the nerves, when 

 irritated by anger ; and, consequently, the saliva secreted and 

 excreted under such circumstances, and inserted in a wound 

 inflicted by an enraged animal, may possibly prevent its cica- 

 trization, and subsequently induce horrid evils. Thus, also, 

 the milk of an angry nurse being disordered and rendered im- 

 pure, may become hurtful to the infant. It appears more diffi- 

 cult to explain what share the nerves have in inducing a morbid 

 coagulation of the blood, or a putrid deliquescence, acrimony, 

 putridity, and impurity of the fluids in a cancerous or gan- 

 grenous part, &c. ; these things posterity may inquire into. 



SECTION VI. DO THE NERVES EXERT ANY INFLUENCE IN THE 



PRODUCTION OF ANIMAL HEAT? 



What opinions various authors have expressed concerning the 

 source and maintenance of animal heat are well known; I think, 

 therefore, I need not detail them. Among them all, that was best 

 received which maintained that animal heat arises from the 

 attrition of the particles of blood with each other, and with the 

 walls of the vessels. After Haller had weighed all the various 

 views, he adopted the theory of Boerhaave, according to which 

 animal heat is acquired by friction, observing : '' Hitherto it 

 seems to me by far the most probable, that the blood acquires 

 heat from motion.^' ^ In the meanwhile, he appears not to 

 have disagreed altogether with the opinion of those who main- 

 tained that the nerves have some share in the production of 

 animal heat ; for he observes, in another place : " I refer heat, 

 which arises from friction, to stimulus.^^^ The objections to the 

 doctrine, that friction is the sole cause of animal heat, raised 

 by De Haen,^ seem to have particularly influenced recent 



' De Part. Corp. Hum. Fabr. et Usu, torn, iv, p. 253. 



^ Ibidtm, p. 159. 



3 Rat. Med., torn. iv. p. 248. 



