Abstract
In former investigations we have shown that the growth-promoting influence of acid extract of anterior pituitary gland of cattle on bone and cartilage of young guinea pigs is exerted without the intervention of the thyroid gland. 1 Correspondingly we wished to determine whether the accelerated healing tendency of fractured bones, caused by the extract, 2 is also independent of the action of the thyroid.
The experiments were carried out in 26 winter and spring guinea pigs, on the average weighing from 120 to 280 gm. Under deep ether anesthesia the tibia and fibula of the right hind leg were broken about the middle of their shafts and bandaged according to the method described previously. Both lobes of the thyroid were completely removed immediately after fracturing. Injury to the parathyroids was carefully avoided. Sixteen of the animals were injected daily with 1 to 11/2 cc. of extract intraperitoneally for periods varying from 6 to 21 days, the first injection being applied immediately after thyroidectomy. Ten guinea pigs were not injected and served as controls. After 6, 10, 14, and 21 days the fractured bones were removed in toto and specimens prepared for microscopical examination as previously described. 3
As to the gross appearance of the callus in the injected and thyroidectomized animals, it was invariably firmer and harder than that of the non-injected thyroidectomized guinea pigs. This fact was noted as early as 6 days after fracturing, but even more distinctly at subsequent periods. In all cases a complete union by a dense, bony, calcified callus had taken place after 21 days, while in the non-injected animals the callus was looser and softer at that period. There was no marked difference in gross appearance between the callus in injected thyroidectomized guinea pigs and in those with intact thyroid glands, which had been injected.
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