An experiment was conducted to consider the metabolism system of histidine, tryptophane, tyrosine of some strains of B. dysenteriae. The following results were obtained: 1. With the B. dysenteriae used, when these amino acids were independently substrated, no analysis took place, but when added with glucose, pyruvate, succinate or ATP, they were oxidized. 2. Under these conditions, it is believed that amino acids analyze first by oxidative deamination of α-amino group, then by decarboxylation. 3. In this case it is believed that glucose, and other added substrates or ATP furnish the energy necessary for the activation of α amino group of these amino acids.