Abstract
Thiouracil in 100 mg. % conc. induced a small but significant inhibition of respiration, measured by the War-burg apparatus, in rabbit bone marrow cells. The effect upon the myeloid elements was striking. Comparison of results with those obtained with the polymorphonuclear cells of rabbit peritoneal exudates indicated that the more immature marrow cells were more seriously affected. Microscopic exam. showed no effect upon cell motility. At-temps to oppose the thiouracil effects with 10 mg. % of pyridoxine in vitro were unsuccessful.