350 REGULATION OF TEMPERATURE 



skin temperature is allowed to drop below a certain value. Any- 

 thing which will prevent muscle from responding to this stimulus 

 will do away with this curative heat production, e.g. curari, 

 alcohol, etc. Young animals which have little muscular develop- 

 ment are, obviously, unable to keep themselves warm by exercise 

 and have to be carefully protected against undue heat loss. 



(b) Increased muscular work ultimately leads to increased 

 catabolism of food material and so, indirectly, to an increase in the 

 quantity of heat liberated. Over and above this amount, however, 

 the result of exposure to excessive cold may be combated by the 

 ingestion of foods having a high energy value. Natives of the 

 colder climates introduce much fatty matter into their diets. 



One may just glance at a problem connected with the above. 

 If the action of any tissue-complex, muscle, liver, etc., results in 

 the liberation of " waste ' heat, is heat then liberated during 

 cerebral activity ? At present, careful investigation has failed to 

 show the production of heat by the brain. It is admittedly true 

 that the head becomes heated during prolonged mental work, but 

 this is accounted for by the increased cranial blood supply blood 

 flowing aw r ay from the extremities and from the viscera to the brain. 



Centre. Since the means adopted for the maintenance of an 

 unfluctuating temperature involve the bringing into play of so 

 many structures and of such a variety of nerves, vasomotor, 

 muscular, secretory and so on, it is plain that a co-ordinating 

 centre is a necessity. Experimental evidence leads one to the 

 conclusion that such a centre exists in the corpus slriatum. Vaso- 

 constriction, shivering, and a rise in rectal temperature result 

 from the stimulation of this structure with a cold object. On 

 the other hand, the application of a warm stimulating point leads 

 to vasodilatation, muscular relaxation, and a fall in body tem- 

 perature. Such results are generally interpreted as indications 

 of the sensitiveness of the corpus striatum to alterations of the 

 temperature of the blood flowing through its capillary system. 



Clothes. The question of the maintenance of the human body 

 in comfort is so closely associated with the nature of clothing that 

 a few physical facts bearing on the nature and value of artificial 

 protective and decorative coverings are not out of place here. 

 Liebig made clear one aspect of the function of clothing, saying, 

 '' Our clothing is, in reference to the temperature of the body, 

 merely an equivalent for a certain amount of food." In other 

 words, if we were to do without the protection afforded by clothing 

 we would have to make good the heat thus lost by eating more food^ 



