SUMMARY 
. 
A quantitative method for the determination of relative 
amounts of vitamin B is described. The work comprises 
eleven comparative studies with a total of thirty-eight varia- 
tions of the basal diet and includes over six hundred quanti- 
tative studies of the growth of young rats. 
An adequate basal ration is described which contains 
optimum amounts of all the food factors necessary for the 
growth of young rats with the exception of vitamin B. 
The most advantageous quantities of milk to feed in order 
to detect possible differences in the vitamin B content were 
8 cc. of skimmed milk or 0.8 gram of skimmed milk powder 
per rat per day when the milk was fed separately from the 
rest of the diet; or 25 per cent. of the total food mixture when 
the skimmed milk powder was mixed with the basal ration. 
Feeding the basal ration under the conditions described 
to experimental animals of suitable age and size and suffi- 
ciently known dietary history, it is believed to be possible to 
detect a variation certainly of 25 per cent. and probably of 15 
per cent. in the vitamin B content of the food tested. 
There was no evidence of destruction of vitamin B in milk 
powder heated dry at 100° C. even when this heating was con- 
tinued for forty-eight hours. When the milk was heated in 
the fluid state for six hours at 100° C. there was appreciable 
destruction of vitamin B. Apparently about one-fourth of the 
vitamin was destroyed. Vitamin B is therefore very stable 
to heating at 100° C. in the dry state, but somewhat less stable 
when heated at the same temperature in water solution. 
