FEEDING EXPERIMENTS WITH ISOLATED FOOD SUBSTANCES. 



13 



The success of the cage methods, as such, is shown by our ability to 

 maintain animals in good health for very long periods in this way. 

 Confronted at the outset with the necessity of ascertaining 

 whether the conditions selected the caging, laboratory environ- 

 ment, consistency of the food and the mode of feeding, etc. were 



B 



A. Sketch of cage used for feeding and collection of urine and feces. Upper figure shows 



outer view of food-and-water-receptacle. (Reduced to one-twelfth natural size.) 



B. Illustration of tube from which daily ration is discharged during each diet period. (Re- 



duced to one-fourth natural size.) 



endurable for the animals under any system of feeding, we under- 

 took control trials with a mixed food in the form of dog biscuit and 

 lard. This was prepared as follows : 



The dry dog biscuits were ground to a moderately fine powder 

 in a mill and usually 70 parts by weight were mixed with 30 parts of 

 melted lard . The mixture when cooled was reduced to a homogeneous 

 paste by passing several times through a meat-chopping machine. 

 In this way the paste was forced through small holes in numerous 

 filaments, to which a rotary motion was imparted, insuring a very 



