102 RESPIRATORY EXCHANGE OF ANIMALS AND MAN 



TABLE XVIII. 



not very nearly related systematically to the temperate ones. Moreover 

 standard conditions were not maintained, and most species of the two 

 first-named genera are more active than those of the two last. 



A systematic study of the possible acclimatization of animals with 

 regard to standard metabolism is highly desirable. 



The Influence of Light. 



A number of observers, notably Moleschott and his pupils [1855], 

 Selmi and Piacentini [1870], Pott [1875], nave found that the re- 

 spiratory exchange of animals is higher in the light than in darkness. 



Moleschott and his pupils working on frogs found an increase of 

 8 to 25 per cent, in the light ; Selmi and Piacentini found on the dog 

 and Pott on the mouse that the different spectral lights had very dif- 

 ferent effects, the respiratory exchange being highest in yellow light 

 and lowest in violet. Moleschott and Fubini [1881] found on frogs 

 that the effect of light was diminished but not abolished when the 

 animals were blinded. In all these experiments muscular movements 

 were not excluded, and the results are probably to be ascribed to an 

 influence on the functional activity of the muscles through the central 

 nervous system and the organs of sense. 



In experiments in which standard conditions have been main- 

 tained no effect of light has been noticed. Experiments have been 

 made by Loeb [1888] on chrysalides of butterflies and by C. A. Ewald 

 [1892] on curarized frogs. Loeb's results are very irregular individu- 

 ally, but on the whole unfavourable to the assumption of an augmenting 

 effect of light upon the metabolism. In Ewald's careful experiments 

 no measurable effect of light could be detected. 



With regard to the fundamental problem the latter experiments 

 are just as inconclusive as the former, because the light never reached 

 the cells in which the metabolic processes take place. Experiments 

 will have to be made on hyaline aquatic animals suitably narcotized to 

 ensure standard conditions. 



