Abstract
In earlier investigations Loeb, 1 and Loeb and Kaplan 2 have shown that the compensatory hypertrophy of the thyroid gland of guinea pigs which takes place after extirpation of a great part of this organ, is very much diminished or entirely prevented if, following the extirpation, daily a tablet of Armour's anterior pituitary substance is fed to guinea pigs. In our first publication, we considered whether the effect observed by us was due to the anterior pituitary preparations as such or to an admixture. Analysis of the action of iodine preparations on the compensatory hypertrophy of the thyroid gland allowed us to exclude the addition of this substance as the cause of the prevention of compensatory hypertrophy. Furthermore, H. A. McCordock 3 showed in this laboratory that Armour's tablets prevent also the marked increase in mitoses in the thyroid otherwise produced by administration of KI to guinea pigs. We had planned several years ago to compare with the effect of Armour's preparation, the effect of oral administration of anterior pituitary of cattle prepared by ourselves from fresh anterior pituitary obtained from the slaughter house. Only within the last year was it possible for us to carry out these plans. We dried the anterior pituitary of cattle after it had been cut into small pieces, and powdered it. Pills were then made from the powdered substance, each pill containing the same amount of anterior pituitary substance as one tablet of Armour & Co. We used for our experiments 54 guinea pigs. From each animal the thyroid lobe of one side and either one-half or two-thirds of the other side was removed. One-third of the animals was fed daily with tablets of the Armour preparation, and a second third was fed with pills prepared in our laboratory, while the last third did not receive anterior substance; it served as a control set.
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