Abstract
THE well-known syndrome caused by a failure of thyroid function has been described in a variety of animals. The effects of thyroparathyroidectomy in new-born rats has been studied quite thoroughly by Salmon (1938), who has observed the usual characteristics of cretinism, i.e., retarded growth, lowered body temperature, sluggish reflexes, awkward muscular movements, persistence of infantile skull proportions, andgreatly retarded skeletal development. As an alternative method of inducing hypothyroidism, thyroid activity can be inhibited or abolished by the administration of anti-thyroid drugs without the side-effects attendant upon surgical operation (MacKenzie and MacKenzie,1943; Astwood, Sullivan, Bissell and Tyslowitz, 1943). In view of this fact, it was decided to determine the effect of the administration of one of these drugs, thiouracil, on the early development of this species. METHODS Rats of the Long-Evans strain were used. Thiouracil2 was administered daily from birth by the subcutaneous injection of a suspension of the fine powder in 0.1 to 0.2 per cent agar.