FEEDING EXPERIMENTS WITH ISOLATED FOOD SUBSTANCES. 



33 



In order to compare the suitability of casein diets containing 

 the salt mixtures recorded above, a series of trials was begun on rats 

 which had previously been under observation in cages so that any 

 eccentricity of eating or of metabolism might be noted. During this 

 preliminary period the diet consisted of the dog biscuit mixture 

 already referred to in the "control" series. During the casein 

 periods the following diets were used, which are indicated in the 

 tables by the corresponding numbers. 



Table XIII. 



Pure casein 



Cane sugar 



Starch (arrow-root). 



Lard 



Agar 



Salt mixture I 



Salt mixture II 



Salt mixture III. . . . 



'3 4 

 20. 6 



23 -7 



35.0 



5-2 



18.0 

 15.0 

 29.5 

 30.0 

 5.0 



10.0 

 4.0 



46.0 

 30.8 



4-4' 



4.8 



18.0 

 15.0 

 29.5 

 30.0 

 5.0 

 2-5 



2. 1 



25 



Nitrogen. 



ioo.o 

 1.87 



100.0 

 2. si 



100.0 

 ..38 



100.0 



2.54 



12.0 



15.0 



30.0 

 30.0 



5.0 



18.0 

 15.0 

 29.5 



30.0 



5.0 



8.0 



2-5 



100.0 

 1 54 



100.0 



2.53 



The records of the animals during the entire course of the experi- 

 ment, until it was stopped by the loss of the laboratory by fire, are 

 shown in Tables XIV-XXII and Charts XI-XIII. 



Table XIV. Summary of Data on Rat XXX, fed on Pure Casein (as the only 

 Protein) and Salt Mixture III for 42 Days. Daily Averages. 



Period i. Dog Biscuit-Lard Diet. 



Date of 

 experiment. 



Intake. 

 Body- 

 weight. 



Food. Nitrogen. 



Nitrogen output. 



N-utilization. 



Urine. Faeces. Total. 



I909. 

 Nov. I . 



8. 



'5- 

 22. 



gm. 

 159.0 

 178. 8 

 191. 3 

 185.6 



gm. 



gm. 



gm. 



gm. 



gm. 



p. ct. 



N-balanee. 



gm. 



9.8 0.158 0.139 0.019 0.158 88 0.000 



10.8 0.180 0.119 0.032 0.151 82 +0.029 



9.3 0.154 0.1 14 0.028 0.142 82 +0.012 



Period 2. Casein DreT i. 



1909. 

 Nov. 29. 

 Dec. 6. 

 '3 



76 



82 



85 



0.018 

 +0.001 



0.005 



Period 3. Casein Diet 2. 



1909. 

 Dec. 20. 



27- 

 1910. 

 Jan. 3. 



90 

 91 



9' 



+0.006 

 +0.01 1 



+0.014 



