4 
Proceedings of the lloyal Society 
Louie acid exhaled by frogs (the Rana esculenta ) is much greater in 
light that in darkness ;* but the most important researches on the 
subject were communicated to the same Society by M. Eeclard in 
1858. From a series of experiments, continued for four years in the 
Laboratory of the Faculty of Medicine, he obtained the following 
results : — f 
1. That the nutrition and development of animals that breathe 
by the skin experience remarkable modifications under the influ- 
ence of the differently-coloured rays of the spectrum. The eggs of 
the fly (flusca carnaria ), placed in six bell glasses, violet , blue, red , 
yelloiv , transparent , and yreen, produced worms which, at the end 
of four or five days, were very differently developed. Those deve- 
loped in the violet glass were triple in size and length to those in 
the green glass, the influence of the other colours diminishing in 
the above order. 
2. That the same weight of frogs produced more than twice the 
quantity of carbonic acid, in respiration, in the green than in the 
red glass. When the same frogs were skinned, the carbonic acid 
was greater in the red than in the green rays. No difference was 
observed with birds, and the small mammalia, such as mice, owing 
to their being covered with hair and feathers. 
3. That the cutaneous exhalation of the vapour of water is one- 
half ox one-tliird less in the daik than in ordinary daylight, or in 
violet light, in which the exhalation is the same. 
Few and imperfect as these observations are, they entitle us to 
inquire into the influence of light upon the human frame, physical 
and mental, in health and disease, in developing the perfect form of 
the adult, and in preserving it from premature decay. In the absence 
of researches which might have been made in our hospitals, prisons, 
and madhouses, we must grope our way among general speculations 
and insulated facts, and we have no doubt that the direct influence 
* 
of light over the phenomena of life will not be found limited to 
the lower races of the animal world. 
Man, in his most perfect type, is doubtless to be found in the 
temperate regions of the globe, where the solar influences of light, 
heat, and actinism, are so nicely balanced. Under the scorching 
* Comptcs Rendus , 1855, tom. lv. pp. 3G3, 456, 643. 
4 lb. 1858, tom. xlvi. p. 441. 
