“…These concentrations are lower, and that in the kidney much lower, than those hitherto reported in hyperthyroid goats from this laboratory (Chanda & Owen, 1952). The known antithyroid action of vitamin A and carotene in a number of species (see books and reviews of Lindquist, 1938;Brody, 1945;Moore, 1957;Goodwin, 1952;Owen, 1941Owen, , 1947Owen, , 1951Owen, , 1954 and the anti-metabolic effect of vitamin A (Leutskii, I 961) make it reasonable to attribute the effect of carotene deprivation on the heart rate of the goat to the damping of the thyroid by dietary carotene. T h e interaction of the thyroid and vitamin A is complex (Chanda & Owen, 1952;Owen, 1962;Chanda, Clapham & Owen, 1955;Paul, Chanda & Chakraborty, 1962) and may be evident only when the intake of carotene is either too great or too small (Frape, Speer, Hayes & Catron, 1959).…”