442 RESPIRATION. 



Influence. of the Season of the Year. It has been pretty 

 well established by the researches of Dr. Smith, that spring- 

 is the season of the greatest, and fall the season of the least 

 activity of the respiratory function. 



The months of maximum are : January, February, March, 

 and April. 



The months of minimum are : July, August, and a part 

 of September. 



The months of decrease are : June and July. 



The months of increase are: October, November, and 

 December. 1 



"W. F. Edwards, in 1819, showed in a marked manner 

 this influence of the seasons upon the respiratory phenomena 

 in birds. In a series of very curious observations, which he 

 repeatedly verified, it was demonstrated that the increase in 

 the activity of respiration during the winter was to a certain 

 extent independent of the immediate influence of the sur- 

 rounding temperature. In the month of January he confined 

 six yellow-hammers in a receiver containing T1'4 cubic inches 

 of air, carrying the temperature to from 69 to 70 Fahr. 

 The mean duration of their life was 62 minutes 25 seconds. 

 In the months of August and September he repeated the ex- 

 periment on thirteen birds of the same species, at the same 

 temperature. The mean duration of life was 82 minutes. 2 



These experiments have an important bearing on our 

 viev 7 s concerning the essential nature of the respiratory func- 

 tion. They seem to indicate that the respiratory processes 

 are intimately connected with nutrition. Like the other nu- 

 tritive phenomena, they undoubtedly vary at different sea- 

 sons of the year, and are to a certain extent independent of 

 sudden and transitory conditions. During the winter, more 

 air is habitually used than in summer, and the respiratory 



1 Resume de Recherches Experimental sur la Respiration. Journal de la 

 Physiologic, 1860, tome Hi., p. 519. 



* W. F. EDWARDS, De V Influence des Agens Physiques sur la Vie, Paris, 1824, 

 p. 200. 



