Studies with a radioactive spinal anaesthetic.

The need for information about the fate of a spinal anaesthetic after its introduction into the spinal theca was early recognized (Miller, 1901), but many years elapsed before the problem was seriously studied by a number of workers, including Stout (1929), Kustner and Eissner (1930), Koster et al. (1936, 1938, 1939), Bullock and Macdonald (1938), and Shields (1942). In the main these workers agreed that after the intrathecal injection of procaine there was a rapid initial drop in local concentration with a subsequent period of gradual decrement. Evidently an anaesthetic departs from the subarachnoid space, but what is its route of depai ture? There are various theoretical possibilities: