44 



FEEDING EXPERIMENTS WITH ISOLATED FOOD SUBSTANCES. 



Despite numerous failures with other proteins than casein, sev- 

 eral experiments have already been continued long enough to hold 

 out promise of the possibility of ultimate success. In these the ani- 

 mals were fed on a mixture in which the casein content was gradually 

 decreased and then entirely replaced by vegetable protein.* 



Rat i 6. This rat, after a preliminary feeding on dog biscuit- 

 lard diet, was fed through Period 2 with a mixture containing casein 

 12, excelsin 6, sugar 15, starch 29.5, lard 30, agar 5 and salt mixture I 

 2.5 per cent. This contained 2.74 per cent of nitrogen. During 

 Period 3 the proportions of excelsin and casein were 9 per cent, 

 the rest of the mixture remaining the same and containing 2.75 per 

 cent of nitrogen. During Period 4 the proportion of excelsin was 

 made 12 and casein 6 per cent, and the diet (otherwise as before) 

 contained 2.8 per cent of nitrogen. Throughout Period 5 the casein 

 was wholly replaced by excelsin, but otherwise the mixture was that 

 above given. The nitrogen content of this diet was 2.94 per cent. 



Table XXVI. Summary of Data on Rat i6, fed for 210 Days on Mixtures 

 Containing Casein and Excelsin as the Only Proteins. Daily Averages. 



Period i, 28 Days. Dog Biscuit-Lard Diet. 



Intake. 



Date of 

 experiment. 



1910. 



Jan. 24. 



3i 



Feb. 7. 



'4 



21 . 



Body- 

 weight. 



gm. 



238.8 



235.2 



225.O 



226.8 



219.5 



Nitrogen output. 



Food. Nitrogen. Urine. 



Faeces. 



gm. gm. 



gm. 



gm. 



Total 



N-utilization. 



N-balance. 



gm. 



p. Ct. 



gm. 



8.4 

 6.5 

 8.5 



5-7 



o. 132 

 o. 106 

 o. 163 

 O. I 10 



o. 103 

 0.084 

 o. 102 



0.088 



0.025 0.128 



0.024 o. 108 



o . 029 o . 1 3 1 



0.018 0.106 



81 



77 

 82 



84 



+0.004 

 o . 002 

 +0.032 

 +0.004 



Period 2, 42 Days. Casein 12 per cent, Excelsin 6 per cent. 



1910. 

 Feb. 28. 

 Mar. 7. 



'4 



21 . 



28. 



4 



Apr. 



90 



84 

 85 



90 



88 

 86 



+0.006 

 +0.028 

 +0.006 

 +0.034 

 +0.025 

 +0.017 



Period 3, 35 Days. Casein 9 per cent, Excelsin 9 per cent. 



1910. 

 Apr. 1 1 

 18. 



25- 

 May 2 . 



9- 



225.5 

 224.0 

 229.5 

 2342 

 240.0 



7-5 

 7.0 

 7.6 



8.5 

 8.7 



0.207 

 0.193 

 0.21 1 

 0.234 

 0.238 



o. 160 

 o. 180 

 o. 172 

 o. 169 



0.175 



0.031 

 0.021 

 0.023 

 0.027 

 0.025 



o. 191 

 0.201 



0.195 



o. 196 

 0.200 



85 

 89 

 89 



88 

 89 



+0.016 

 o . 008 

 +0.016 



+0.038 

 +0.038 



*For a description of the vegetable proteins used see Osborne; Die Pflanzenpro- 

 teine, Ergebnisse der Physiologie, 1910, x, p. 47. 



