312 



and he has found that the amount of carbonic acid given oif by different 

 animals in proportion to their weight in a given time was subject to con- 

 siderable variation, dependent upon the species and the existing physi- 

 ological conditions. His investigation consists of two parts: 



First, estimation of the weight of the animal experimented upon, 

 both before and after the experiment, the duration of the experiment in 

 hours and minutes, the amount of carbonic acid separated during the 

 experiment, and from the data thus obtained he calculates the final 

 results for a period of six hours and for a given weight of animal, (100 

 grams.) Finally, he notes the consumption of air and the temperature 

 of the room during the experiment. 



Second, estimation of the amount of carbonic acid liberated in a given 

 time by different animals under the influence of different colored light. 



The animals experimented upon belonged to the mammals, birds, fishes^ 

 amphibians, insects, snakes, and worms, and with reference to the amount 

 of carbonic acid eliminated in a given time they may be divided into 

 two distinct groups; the mammals, birds, and insects constituting the 

 first group, and the fishes, amphibians, snakes, and worms the second. 

 Of the first group the birds liberate the largest relative amount of car- 

 bonic acid. The mammals range next to the birds, and the fishes liber- 

 ate the smallest amount. The animals of group two liberate a much 

 smaller relative amount than group one, and of this group the worms 

 give off' the largest and the snakes the smallest quantity. While in the 

 air the aquatic animals of this group liberate a greater quantity than 

 the other animals of the group, and a much smaller quantity while in 

 the water. 



The amount of carbonic acid set free depends largely upon the age of 

 the animal, it being much gTeater in case of young than in old animals. 

 But while this may be accepted as a general rule, an exception may be 

 found among the insects, when the reverse is true, since the insects in 

 the larval condition give off' less carbonic acid than when fully devel- 

 oped. In case of the amphibians the amount liberated by young ani- 

 mals sometimes reaches three or four times, and even more than four 

 times, that liberated by the old ones. 



Sex also influences this action, it being more marked in the male 

 than in the female sex. But the weight of the animal and the indi- 

 viduality hg^ve no influence upon it, and while the varieties in species 

 must exert a not unimportant influence upon the quantity liberated and 

 must produce some variation, the amount of this variation, in animals 

 nearly allied to each other, is confined to very narrow limits. 



The second portion of the investigation gave the following results : 



Animals give oft" more carbonic acid when subjected to the influence 

 of colored light than in daylight. Of the colored rays the violet and 

 red rays exercise the mildest influence, the green and yellow and the 

 white and blue medium. These results conflict with those obtained by 

 B6chard, but are confirmed by those of Selmi and Piacarlini. Experi- 

 menting with animals (dogs, doves, and cats) in air-tight chambers into 

 which only light of a given color could penetrate, the latter investiga- 

 tors found, by estimation of the carbonic acid eliminated in a given time, 

 that the relative quantities given off under the influence of different 

 colors, were as follows : White, 100 ; black, 82.07 ; violet, 87.73 ; red^ 

 92 ; blue, 103.77 ; green, 100.03 ; yellow, 120.03. Analogous results were 

 •obtained in experiments with other animals. The average results ob- 

 tained by the author in his experiments were as follows : Violet, 86.89;: 

 red, 93.38; white, 100; blue, 122.03; green, 128.52; yellow, 174.79. 



