THE INFLUENCE OF PHYSICAL FACTORS 91 



curve resembles closely that of a small warm-blooded animal. Marie 

 Parhon finds further that the temperature in the cluster of bees inside 

 the hive shows a very striking constancy throughout the year. The 

 average value for each month varies only between 34*1 (July) and 

 3 1 '8 (October). During the winter (December, January, and February) 

 it remains at 32-4. The temperature regulation of the bee cluster (but 

 by no means of a single isolated bee) must, according to this author, 

 be considered as just as perfect as that of a mammal or bird. 



That the cluster of bees in winter generates a large amount of heat 

 has been shown also by Phillips and Demuth [1914] who did not observe, 

 however, the absolute constancy claimed by Mile. Parhon. 1 According 

 to Phillips and Demuth the temperature in the hive fluctuates with the 

 outside temperature until it falls to 57 F. (14 C.) when the bees form 

 into a compact cluster in which heat is generated and a higher tem- 

 perature maintained. " The nearly spherical cluster of bees . . . con- 

 sists of an outer shell of bees close together with their heads towards 

 the centre. This ring may be several layers thick. The bees in this 

 outer shell are quiet except for an occasional shifting of position. In- 

 side this rather definite shell the bees between the combs are not so 

 close together nor are they headed in any one way. Considerable 

 movement, such as walking, moving the abdomen from side to side, 

 and rapid fanning of the wings takes place inside the sphere, and when 

 a bee becomes unusually active the adjoining bees move away leaving 

 an open space in which it can move freely." The temperature in the 

 centre of the cluster was in one case recorded as being 75 F. (40 C.) 

 higher than outside it at a distance of 4 J inches. 



WARM-BLOODED ANIMALS. 



In intact warm-blooded animals a fall in the surrounding tempera- 

 ture regularly causes not a decrease but an increase in the respiratory 

 exchange thanks to the mechanism of " chemical heat regulation". 

 This has been shown over and over again by Zuntz and Rohrig [1871], 

 Pfluger [1876, 1878], Colasanti [1877], Voit [1878], Carl Theodor 

 [1878], and several others. The most elaborate study of the chemical 



1 They lay stress upon the importance of not in the least disturbing the bees. As Mile. 

 Parhon went on putting thermometers into the hive until she found the highest temperature 

 the bees must have been greatly disturbed, and her figures probably indicate the maximum 

 temperature which the bees can be induced to set up. 



