62 Feeds and Feeding. 



blood in tlie bodies of these animals decreased somewhat on long 

 confinement in a dark room. The average quantity of blood in 

 the animals kept in the light was 22.2 grams, and of those kept 

 in a darkened room, 17.2 grams. In another experiment, the 

 bodies of rabbits kept in light and dark rooms contained 100. o 

 grams and 90.6 grams of blood, respectively. According to these 

 experiments, darkening the stable will have a stimnlating influ- 

 ence on the formation of fat in the bodies of animals. Graffen- 

 bferger also ascertained that the production of fat in animals kept 

 in the light and those kept in the dark was as 100 : 126 for the 

 first 16 days. After 46 days the ratio was as 100 : 119. With 

 full-grown animals the increase was as 100 : 216 after 24 days, 

 and as 100 : 138 after 75 days. 



The deprivation of daylight, therefore, caused an increase va 

 the formation of fat and an increase in live weight. The increase 

 was larger in the case of fall-grown animals than with younger 

 ones; and further, by prolonging the absence of light the increase 

 was relatively smaller than for the shorter time. As the develop- 

 ment of the skeleton and liver of the animal is retarded by dark- 

 ness, the prolonged absence of light has a deleterious effect upon 

 the health of the animal. While Graffenberger corroborates the 

 results of Moleschott, ' Platen, ^ and other early investigators, that 

 light causes an increased excretion of carbonic acid and a greater 

 consumption of oxygen, he finds that protein consumption is not 

 influenced by the absence or presence of daylight, 



1 Wien Med. Wochenschr., 1856, No. 43. 

 » Pfliiger's Archiv, 11, p. 272. 



