Abstract
Extract
Farmers and stock firms have suggested that “fine particle” phenothiazine is toxic, despite work (Whitten, Citation1956) which has shown that phenothiazine of 10-micron particle size is a more efficient parasiticide than coarser material. The writer was fortunate in obtaining phenothiazine of a known particle size, and attempted to determine toxicity with doses of 15 gm., 75 gm., and 120 gm., using the samples provided.