1. Liver extract powder, No. 343 Lilly, and the same material prepared for parenteral use, when administered daily by mouth in amounts derived from 2.5 gm. of fresh whole liver, to rats weighing from 40 to 50 gm., contain sufficient vitamin B1 to support normal growth, provided the animals receive in addition an adequate amount of vitamin B2 G. Moreover, liver extract in the forms mentioned, administered in the same amounts, does not contain sufficient vitamin B2 G to maintain normal growth of similar rate when all other necessary constituents of the diet are provided.

2. Liver extract (Lilly) in the form prepared for parenteral use, when administered daily by intraperitoneal injections, in amounts derived from 2.5 gm. of fresh whole liver, to rats under standard experimental conditions, does not contain sufficient vitamin B2 G to maintain normal growth. Furthermore, the amount of vitamin B1 present in liver extract in this form is not as effective in supporting normal growth when given by intraperitoneal injection as it is when given by mouth.

3. Vegex, when administered daily in amounts of 50, 150, and 250 mg. to rats of 40 to 50 gm. in weight contains sufficient vitamin B1 to maintain normal growth of the rats, provided the animals receive in addition an adequate amount of vitamin B2 G. However, vegex in the same amounts does not contain sufficient vitamin B2 G to support normal growth of similar rats when all other necessary constituents of the diet are provided.

4. These experiments indicate that the extrinsic, anti-anemic factor of Castle and the thermostable growth-promoting food constituent, commonly known as vitamin B2 G, are not identical.

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