ACTION OF THE TROPICAL SUN. 



107 



dogs have no sweat glands, the evaporation of water, which in men is 

 brought about by the secretion of sweat, is replaced in these animals by 

 increased evaporation from the surfaces of the lungs, mouth, and 

 especially the tongue. 



However, in spite of the increased water evaporation, the body tem- 

 perature measured in ano of the dog in the direct rays of the sun for 

 several hours may rise 0°.5 to 1°. If the temperature is measured by 

 inserting a thermometer or a thermopile into the subcutaneous tissues 

 through a small incision of the skin, the subcutaneous temperature is 

 found to be above 40°. 



In a number of experiments, two comparable rabbits in each instance 

 were kept side by side a few paces apart, one in the shade of a house or 

 a wooden wall, the other exposed to the sun. The animals in thd sun 

 died in from one to three hours, the temperature in ano rising to febrile 

 heights, the subcutaneous temperature in the sun increasing considerably 

 above that simultaneously taken in recto. The animals in the shade 

 behaved normally, their temperatures increasing but slightly. 



Table II. — Temperature, subcutaneous and rectal, of rabbits in the sun and shade. 



Date. 



Remarks. 



Time. 



Temperature of 

 rabbit in sun. 



Temperature of 

 rabbit in shade. 



Tem- 

 pera- 

 ture 



Black-bulb 

 thermom- 

















Subcuta- 

 neous. 



Rectal. 



Subcuta- 

 neous. 



Rectal. 



air m 

 shade. 



eter. 









°C. 



°a 



°C. 



°C. 



°C. 









7.55 a.m. 



36.8 



37.5 



36.4 



37.6 





42° at 11 







8.15 a.m. 



37.8 



37.3 



36.5 



37.4 



11. i 



a. m. 



1910. 





8.30 a.m. 



38.3 



37.3 



36.5 



37.5 



27.5 





Oct. 12 



Two white rabbits. 



8. 45 a. m. 



39.1 



37.8 



36.8 



37.4 



29.6 







In animal house. 



9.00 a.m. 



39.2 



38.8 



36.8 



37.5 



30.0 







Exposed 8 a. m. 



9.15 a.m. 

 9. 30 a. m. 



39.8 

 40.8 



39.0 

 39.2 



36.8 

 37.9 



37.6 

 37.9 



29.4 

 30.7 









9.45 a.m. 



41.9 



40.6 



38.0 



38.0 



30.5 









9.50 a. m. 



J Experiment c 

 1 



iiscontinued, an 

 aken in. 



mals 





Oct. 18 



Two brown rabbits. 



,8.20 a.m. 



36.5 



38.0 



36.4 



37.7 



— 



54° at 11 





In animal house. 



8. 50 a. m. 



40.7 



39.0 



36.5 



37.5 











Exposed 8.25 a.m. 



9.20 a.m. 

 .9.50 a.m. 



44.5 

 Animal 



42.3 

 dead. 



37.6 

 37.9 



37.8 

 38.1 







Under the climatic conditions surrounding our experiments the num- 

 ber of calories lost depends mainly on the amount of water evaporated 

 in a given time. A dog, by its peculiar hyperpnoea can evaporate rel- 

 atively more water, and thus lose more heat than the rabbit. However, 

 if we tracheotomize the animal this evaporation is inhibited. The 

 expired air escapes through the tracheal cannula, so that the water vapor 

 carried with the current can not reach the surface of the tongue, and 

 therefore there is but a limited surface from which it can be evaporated. 



