66 APPLIED PHYSIOLOGY 



or of toxic doses of alcohol, and, as Watson says, * there 

 is too much reason to believe that poor wretches who 

 have been picked up by the constables in the streets at 

 night during periods of hard frost have been supposed to 

 be drunk, when in truth they were only stupefied by cold.' 



The nervous mechanism which calls out an increased 

 production of heat by the muscles, however, is not thrown 

 into action in a purely reflex way. In part it is a volun- 

 tary process, active movements being performed instinc- 

 tively in order * to keep one's self warm.' In part also 

 it is a subconscious 'psychical reflex,' comparable to that 

 which leads to blinking of the eye on any sudden 

 menace to the cornea, and which leads to more or less 

 involuntary shivering i.e., slight but rapid muscular 

 contractions and which can be more or less completely 

 inhibited by the will. Short of actual shivering, cold 

 seems, through nervous action, to raise the ' tone ' of the 

 muscles, and therefore to increase the volume of heat 

 they produce (see p. 22). Everyone feels more 'strung 

 up ' on a cold day, and this is what is really meant when 

 a cold climate is spoken of as ' bracing.' It has, in fact, 

 a tonic effect very like that of strychnine. 



Whether or not there is a special centre in the brain 

 which presides over the function of heat production is a 

 point on which physiologists are not yet agreed, though 

 the bulk of opinion is opposed to such a conclusion, in 

 spite of the experimental and clinical evidence which 

 points to the existence of such a centre in the corpus 

 striatum. On the whole, it seems more probable that 

 the control is exerted through the medium of the 

 ordinary motor andvasomotor centres. There can be 



