OBSERVATIONS ON THE BIOLOGICAL VALUE OF A MIXTURE OF ESSENTIAL AMINO ACIDS.

(1) A mixture of "essential" amino acids, fed to rats, was found to be inferior from a nutritional point of view to enzymatic or acid casein hydrolysates or casein fed at comparable levels. (2) Evidence is presented which suggests that the nutritive inadequacy of the essential amino-acid diet may be due in part to toxic effects of unnatural forms of certain amino acids that can not be utilized.