THE EXTERNAL ENVIRONMENT 255 



are still disputed. In particular, it is not absolutely proved 

 that luminous radiation raises the rate of the respiratory 

 exchanges, increasing the consumption of oxygen^ 1 ) 



However, light is a muscular excitant, ( 2 ) and it is incontestible 

 that it is a cell-stimulant. In fact, it assists the development 

 of the body and in particular the organ of sight. ( 3 ) It determines 

 the pigmentation of the skin, and it appears to assist the multi- 

 plication of red corpuscles. 



On the contrary, darkness impedes the development of the 

 organs, atrophies that of the sight, depigments the skin ( 4 ), and 

 lowers the number of red corpuscles. ( 5 ) The general sensibility 

 of people who live in the dark is blunted, so much so that the 

 return to light causes shock, ( 6 ) and the muscular power diminishes 

 as in the case of the blind. ( 7 ) Colours seem to have various effects 

 on the subject, although it is not proved that they modify the 

 respiratory exchanges ( 8 ) or the rate of development of the 

 organisms. ( 9 ) It is not, either, quite certain that their influence 

 on the psychic state of man, is constant. It is said to have been 

 found that in photographic developing rooms men working in 

 a red light were ga}/ and talkative, whilst in a violet light they 

 became melancholy" and apathetic and less disposed to work. 



The violet and ultra-violet rays of the spectrum exercise a 

 chemical action, which is probably the important factor in the 

 phenomena of pigmentation. These rays abound in electric 

 light and cause various diseases such as electric opthalmia ( 10 ) 

 and facial erythemia, aggravated sometimes by cerebral conges- 

 tion. Sources of light that are very rich in ultra-violet rays can 

 cause veritable sunstrokes. 



188. The above remarks apply to solar radiation. The sun 

 gives out a flood of radiations. It has a beneficial (microbicide) 

 effect, but its chemical rays can cause sunstrokes.f 11 ) By using 



(M Moleschott admitted it and also Fubini (Arch. Ital. Biol., 1891, vol. 

 xvi., p. 80). Against it are the works of Speck (Arch. f. Exper. Path. Und 

 Pharmak, 1880, vol. xii., p. 1) Adducco, Loeb, etc. 



( a ) D'Arsonval (Comptes Rendus Biologic, 1891, p. 318). 



( 3 ) W. Edwards, Influence des Agents Physiques sur la Vie, 1824 : Hum- 

 boldt ; Vicarelli ; (Ann. d. Ostetr. e. Ginecol., 1890). 



(') Armand Vire (Comptes Rendus Acad. Sc., 14th March, 1904). 



( 6 ) Kronecker Marti (he. cit.}. 



( 6 ) See an article, Nature, llth May, vol. Ixxxv i., p. 349, 1911. 



( 7 ) Griesbach (Pfl. Arch., 1899, vols. Ixxiv.-v.) ; Fere Travail et Plaisir, 

 p. 100 (loc. cit.}. 



( 8 ) Selmi et Piacentini (R, 1st lomb. d. Sc. e Lett., Rendic., 1870, pp. 57-63). 

 () E. Yung (Comptes Rendus Acad. Sc., 1880, vol. xci., p. 440). 



( 10 ) Terrien (Arch. d'Ophtalm., 1902, p. 692, 1908, p. 679). 

 ( u ) Widmark (Skand. f. Physiol., i., p. 264 ; iv., p. 281) ; Ch. Bouchard 

 (Comptes Rendus Biologie, 1877). 



