THE EFFECT OF ADMINISTRATION OF SMALL AMOUNTS OF THYROID GLAND ON THE SIZE AND WEIGHT OF CERTAIN ORGANS IN THE MALE WHITE RAT

¹ The Physiology Department, The University, St Andrews

An alteration in the size of various internal organs, produced by administration of small amounts of fresh thyroid, was determined by direct weighing and comparison with the weights of normal organs in rats of the same length.

The results obtained have been compared with those of Herring and of Hoskins, and the points of resemblance and of difference noted as follows:—

The observations of the former are confirmed except in the case of the pituitary. In the experiments now recorded a hypertrophy of the gland was noted in the majority of animals examined, while Herring found a decrease in size under similar conditions when investigating this point in male rats.

Hoskins arrives at no conclusions as to the effect of thyroid exhibition on the size of the animal's own thyroid. The results brought forward in the present communication show a conspicuous diminution in the weight of this gland. The other conclusions of Hoskins are confirmed.

The quantitative alterations in size of the internal organs produced by thyroid administration have been considered at varying intervals after resumption of normal diet, and it is argued that a tendency is shown for this abnormal condition to be temporary, and that a return, perhaps incomplete, to normal proportions is indicated after cessation of thyroid feeding.

It was further noted in one case that a gradation in alteration in size is seen when the percentage increases or decreases are arranged in order according to the time elapsed after administration of thyroid. In the other series this gradation is not so well marked, and possibly may, in part, be due to the fact that these animals were in the habit of spilling quantities of food at various times, and there is thus no guarantee that the full dose of 0·1. grm gland was in all cases consumed each day.