EFFECT OF LIGHT ON THE ORGANISM. 249 



conditions of liglit and temperature: so that if less is 

 expired during night than during the day, the reason 

 cannot be sleep, but the absence of light.* 



Now, we understand why men are sickly and stunted 

 who live in narrow streets, alleys, and cellars, compared 

 with those who, under similar conditions of poverty and 

 dirt, live in the sunlight. And to give a solid basis to 

 such views, we have Moleschott's striking experiments, 

 which prove that under precisely similar conditions of 

 warmth, age, size, food, &c., the single variation in the 

 condition of light produces an equivalent and constant 

 variation in the amount of carbonic acid expired. In 

 bright sunlight as much as one-fifth more carbonic acid 

 was expired than in feeble light.-f- And have not all 

 farmers and cattle-breeders unconsciously paid tribute 

 to this principle, by keeping their animals in the dark 

 to fatten them ? 



Returning from this wide-sweeping excursion to the 

 point from which we started, namely, the love of dark- 

 ness manifested by our animals, the question arises. 

 How can the paradox be reconciled ? One might ven- 

 ture on an hypothesis, were but the facts a little less 

 refractory : when, however, we see one kind of Anemone 

 flaunting in the light, and another creeping under a 

 stone ; when we see the Crab impatient of the day, and 

 the Prawn swimming gaily in the brilliant pool ; when 



* MoLESCHOTT, Liclit UTid Lehen, p. 22, citing the experiments of 

 Booker. 



+ See his Untersiichungen zur Nahirlelire des Menschen ^l. d. Thiere, 

 i. 12. Also his Memoir e in the Annales des Sciences, 185G. 



