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Investigations of the ductless glands during the past 10 years which have required removal of the thyroid, parathyroids, thymus, spleen, suprarenals, and gonads alone, or in several combinations, have afforded us the opportunity of studying some of the effects of such insufficiencies on the remaining tissues of rabbits. The material accumulated under our immediate direction now seems sufficiently extensive to permit of certain statistical studies. In this paper we will report only the data relative to the effect of thyroidectomy, splenectomy, suprarenalectomy, gonadectomy, and combinations of these gland removals on the thymus gland as measured by its involution, persistence, or regeneration? Lymphoid tissues other than the thymus are also affected and will be referred to briefly. The data of 373 protocols have been included in this study. In sorting ,the material, protocols have been discarded for one or another of the following reasons: (1) animals with chronic infections (except snuffles), (2) animals which survived a given operation less than 2 weeks, (3) animals for which the notes of the gross or microscopic examination of the necropsy tissues were incomplete, and (4) animals on which the operation or necropsy was performed by individuals other than the authors. Of more importance than all of these factors of elimination in determining the value of such records, of 1 All operations were performed under ether anesthesia. 429 on

PROCEEDINGSlowing tentative conclusions : Irradiation of 2 proteins, casein, and egg-white, in the dry, solid state changes them so that digestion in vitro by pepsin and trypsin are slightly inhibited. Metabolism experiments on young male rats, on the other hand, demonstrate a slightly higher body-weight when the protein fraction is irradiated. Since the nitrogen-retention on the low protein diet is slightly less for the irradiated than for the non-irradiated protein, the improvement of the body-weight curve appears to be due to something other than improved utilization of the protein. Vitamin D as an antirachitic agent is ruled out since the diet contains an ample supply for that purpose. Some other factor, stimulating in character is suggested.The immediate cause of thyroid hyperplasia in all probability is a relative or an absolzbte deficiency of iodine.' The fundamental or essential cause of goiter is unknown, but the search for the essential cause, as we have often suggested, appears to resolve itself into determining the cause or causes of the iodine deficiency. As most iodine deficiencies are relative rather than absolute, the search further limits itself largely to determining the factors which create the increased needs of the organism for the iodine containing hormone. The simplest way of increasing the need of the thyroid for iodine would be by depressing the utilization of oxygen in the tissues, and the discovery by Chesney and Webster2 that the prolonged feeding of cabbage caused thyroid hyperplasia in rabbits appeared to offer a practical means of testing this hypothesis.It has been shown that there are great seasonal and climatic variations in the goitrogenic activity of cabbage,s that drying in a current *Aided by a grant from the Ella Sachs Plotz Foundation. t

In order further to test our hypothesis that the elements of group VII are selectively filtered from the blood and concentrated by the thyroid gland, rats were injected with Mn54, Br82 and Tc99. The distribution of these nuclides in tissues was determined 2 hours after administration. The thyroidal concentration of Mn54 was about 10 times that of serum, of Br82 1.3 times that of blood and of Tc99 11–30 times that of blood. These results together with those previously reported by us and by others show that ions of all group VII elements are concentrated by the thyroid, though to a varying extent. A study of the effect of stable seventh group ions on the uptake of Mn54, Br82, I131 and Re186 shows that large amounts of F–, Mn++ and Br– have little influence while even small quantities of I– or of Re++ markedly lower the thyroidal uptake of the heavier ions. Only a slight affinity of the thyroid for F–, Mn++, Br– is thus indicated, while that for I– and Re++ is far greater. This conclusion is substantiated by another type of experiment in which pairs of these nuclides were administered simultaneously and the fraction of each taken up by the thyroid determined. The affinity of the thyroid for Te, I and Re proved to be roughly equal and much larger than for Mn or Br. Unlike other group VII elements Mn accumulates in tissues of endodermal origin to an even greater extent than in the thyroid.

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