THE RESPIRATION OF AN INLAND LAKE 337 



THE RESPIRATION OF AN INLAND LAKE 1 



By Proffssor E. A. BIRGE 



SECRETARY OF THE COMMISSIONERS OF FISHERIES, WISCONSIN 



AN inland lake has often been compared to a living being, and this 

 has always seemed to me one of the happiest of the attempts to 

 find resemblances between animate and inanimate objects. Unlike 

 many such comparisons, which turn on a single point of resemblance 

 and whose fitness disappears as soon as the objects are viewed from a 

 different position, the appropriateness of this increases rather than 

 diminishes as our knowledge both of lakes and of living beings is 

 enlarged. 



The lake, like the organism, has its birth and its periods of growth, 

 maturity, old age and death; and this fact is an obvious one, for of all 

 the larger features of the landscape, the lake is the youngest and the 

 most temporary. Its birth lies in the recent past, and in no very long 

 space of time its existence must come to an end. In any lake dis- 

 trict, lakes may be found in all stages of maturity and decay, and many 

 dead lakes will be seen — places where lakes once existed which are now 

 extinct. Lakes show not only the cycle of individual existence, but 

 also the rhythm of seasonal activity. The activity of the lake in sum- 

 mer, both physical and vital, contrasts sharply with its torpidity in 

 winter. And the lake resembles the organism not only in its annual 

 recurrence of activity. The comparison may be pushed farther and 

 extended to the minor fluctuations of the vigor of vital manifestations 

 which characterize lake and organism alike. 



In all these points, and in many others, the lake resembles a living 

 being; but in no respect does it resemble an organism more closely 

 than in the topic on which I am going to speak to you, namely, its 

 respiration. In this comparison, the resemblance is rather in processes 

 and operations than in form. The lake is morphologically a very 

 simple creature, resembling rather a gigantic amoeba than a more 

 highly organized being. Perhaps it would be better to compare the 

 lake, for the purpose of this subject, not with the organism as a whole, 

 but with the special respiratory substance of the animal — the blood. 



Like the blood of the higher animals, the lake consists of an un- 

 organized fluid — the plasma of the blood and the water of the lake — 

 and of numerous organized and actively living parts — cells in the case 



Address of the President at the Thirty-sixth Annual Meeting of the 

 American Fisheries Society, Erie, Pa., July 23-25, 1907. 



vol. lxxii. — 22. 



