228 The Function of Respiration at Various Altitudes. [June 19, 



grms. of these animals emitted in 24 hours in the light 654 mgrms. 

 carbonic acid, and in darkness 522, giving the proportion of 1 to 

 l - 25, the increase of temperature accompanying the light's influence 

 only amounted to 2° 93 C, so that it could not be considered as 

 having exerted any influence. In another paper (same vol. " Compt. 

 Rend.") Moleschott determines the degree of the light used in his 

 experiments by means of photographic paper exposed for five minutes 

 to the light, and compares the depth of tint obtained with standard 

 colours. He finds that the carbonic acid produced under a feeble 

 degree of light is to that exhaled under a very powerful light as 

 1 : 1'18, the increase of temperature being only by 1°'65 C. He 

 concludes : — 1. That frogs for similar weights, and in equal periods, ex- 

 hale from one-twelfth to one-quarter more carbonic acid when breathing 

 under the influence of light than while in the dark, so long as the 

 temperatures are equal or vary but slightly. 2. The production of 

 carbonic acid increases in a direct ratio with an increase of the light 

 to which the animals are submitted. 3. The influence light exercises 

 towards increasing the amount of carbonic acid emitted, acts partly 

 through the eyes, partly through the skin. 



Our knowledge on the influence of light upon the growth of 

 animals, has been extended quite lately by the interesting experiments 

 of Emile Young, of Geneva.* The favourable influence of violet and 

 blue light on the nutrition of animal tissues is clearly demon- 

 strated in that paper. He cites M. Beclard who, in 1858, observed 

 that the worms from flies' eggs acquired growth in violet and blue 

 light much more rapidly than in white and green light. Mr. Emile 

 Young, by experimenting on frogs' eggs, observes that tadpoles 

 become developed much more speedily in violet and blue light than in 

 red and green light, and, moreover, that when grown in white light, 

 and then exposed without receiving any food to the influence of 

 coloured lights, they die soonest under the violet rays. He also states 

 he has seen that tadpoles reared under violet light resist starvation 

 longest if placed afterwards under white light. He concludes that 

 violet light apparently promoted the nutrition of tadpoles more than 

 any other coloured light. An allusion is made in his paper to the ex- 

 periments of General Pleasanton, who found, by keeping young sows 

 under violet and white glass during six months, that those under the 

 violet glass gained, for equal weights, 34 lbs. more than those under 

 white glass. Experiments on oxen by the same author yielded similar 

 results. 



From this mass of experimental work bearing on the influence of 

 heat and light on animal combustion, it may be concluded : — 1. That 

 an increase of temperature causes, or strongly predisposes to a 



* Emile Young, "Influence des Lumieres Colorees sur le Developpement des 

 Animaux." "Archives des Sciences Physiques et Naturelles," Mars, 1879. 



