By means of the chromatography on the 150×0.9cm column of Dowex 50-x 4 author estimated various free amino-acids and related compounds isolated from such sites of the brains of dog as the cerebral cortex, white matter, cerebellar hemisphere, caudal nucleus, thalamus, hypothalamus, medulla oblongata, and cerebellar worm; and obtained the following results: 1. It has been found that the content of glutamic acid is low in the white matter, hypothalamus and medulla oblongata, while the aspartic acid content is likewise somewhat low in the white matter but quite high in the medulla oblongata. The content of γ-aminobutyric acid is markedly high in the hypothalamus, followed by that in the cerebellar worm, but in is low in the white matter. 2. The contents of cystathionin and glutathion are markedly high in the thalamus and hypothalamus. 3. The content of N-acetylaspartic acid is high in the cerebral cortex while it is low in the white matter and medulla oblongata.