458 



PRINCIPLES OF GENERAL PHYSIOLOGY 



of heat is thus shown to be acted upon, as well as the loss of heat. Barbour 

 and Wing (1913) have found that certain drugs known to produce fall or 

 rise of body temperature, such as antipyrin, or /2-tetra-hydro-naphthylamine, 

 respectively, act, when applied to the centre itself, in much smaller amount than 

 when given intravenously. Antipyrin causes fall of temperature with increased 

 respiration and, occasionally, vascular dilation in the ear of the rabbit ; quinine 

 behaves similarly, with more marked vascular dilation. /3-tetra-hydro- 

 naphthylamine, on the other hand, causes rise of temperature, some shivering, 



39" 



38" 



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24 25 



22 23 24 25 26 27 28 



Fro. 140. CHANGES OF BODY TEMPERATURE PRODUCED BY WARMING AND 



COOLING THE H"EAT CENTRE IN THE REGION OF THE CORPUS STRIAT17M OF 

 THE RABBIT. 



Ordinates body temperature in degrees centigrade. 



Abscissae time in hours. 



A. From one hour after insertion, at the arrow, of the tube apparatus for wanning and cooling 



the centre to five hours. Rise of temperature produced by the injury. 

 During the period marked by the thin line above the curve warm water passed through 



tube. The temperature of the body/a/fo. 



During the period marked by the thick line below curve cold water causes rite of temperature. 

 A second passage of warm water produces a, fall, 

 During the night (dotted line) the fever due to the puncture of the centre returned, but was 



reduced by warming the centre again. 



B. The fever produced by the puncture gradually subsides and had disappeared next day. It 



was brought back by cooling the centre (thick line). An intermediate short period (thin 

 line above) shows a rapid effect of wanning. 



(After Barbour. ) 



great vascular constriction in the skin and restlessness, the effects on the heat 

 centre being probably mixed with those on other centres. 



Evolution of Temperature Regulation. According to the experiments of 

 Vernon (1897), the carbon dioxide output of cold-blooded animals does not 

 increase and decrease uniformly with increase and decrease of external temperature. 

 There appears to be a region of temperature in which the output is nearly 

 constant. Thus, on warming newts or earthworms from 10 to 22 '5, there is no 

 increase in carbon dioxide output. This indicates some kind of control over heat 

 production, probably in muscle, on the part of nerve centres more or less sensitive 

 to change of temperature. A further stage of regulation is shown by the 



