450 THE REGULATION OF TEMPERATURE 



tropical dwellers cut down their protein intake (specific dynamic 

 action). 



(c) Subjection of an animal to great external heat leads not only 

 to a disinclination to do external work or to take food, but definitely 

 decreases the flow of the digestive juices. A dog with a gastric 

 fistula (Pavlov, q.v.) gave neither a psychic nor a hormonic flow 

 of gastric juice when its body was overheated. 



One may just glance at a problem connected wdth 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 away 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 striatum. 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 })ody 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. 



Ventilation. The purpose of ventilation is to provide such a 

 change in the air of rooms, that the cooling power of the atmo- 

 sphere of the rooms shall be suitable for the nature of the work 

 being done. Some experiments by L. Hill make this perfectly 

 clear, and show how erroneous were the older ideas concerning 

 ventilation. A mmiber of healthy young men were crowded into 

 an airtight cabinet, provided with an electric fan, and with the 

 necessary apparatus for sampling the air for analysis, etc. " After 

 44 minutes the dry-bulb thermometer stood at 87° F., the wet 

 bulb at 83° F. The carbon-dioxide had risen to 5-26 per cent. 

 The oxygen had fallen to 15-1 per cent. The discomfort felt was 

 great ; all were wet with sweat and the skin of all was flushed. 

 The talking and laughing of the occupants had gradually become 

 less and then ceased. On putting on the electric fan and whirling 

 the air in the chamber the relief was immediate and very great, 



