The author have studied on the histological distribution of thiamine in the nervous tissues of human beings, monkeys, rabbits and albino rats. The following resuts were obtained : 1. In the brain and spinal cord thiamine was found richer in nerve cells than in nerve fibres, and in glia cells the vitamin was less than in nerve cells. 2. The vitamin content of nerve cells in the brain and spinal cord varied according to their functional states and locations. 3. In the ganglion thiamine distributed much in nerve cells, but poor in capsule cells. No difference of thiamine distribution was found among the kinds of nerve cells, but remarkable differences were found by functional conditions. 4. In the peripheral nerve fibres thiamine was less compared with central nervous tissues, but histologically thiamine found much in the axon and less in medullary sheath, but abundant in the Ranvier's node which was an entrance of the vitamin and inorganic substances etc.