Abstract
Conclusions
Our experiments tend to reconcile the differences between the results obtained by Chouke and Irsigler, and our results confirm those of Irsigler as to the necessity of using relatively small doses and short periods of time in order to obtain stimulating effects on the thyroid of the rat by the administration of KI. There seems to exist a quantitative relation between the increase in mitotic proliferation and the quantity of KI used and the length of time during which it acted. In the case of the guinea pig we have shown previously that within the limits tested the larger doses are more effective than the smaller ones. Whether a similar relation exists also in the ease, of the rat thyroid remains to be seen. It is of interest that the maximum number of mitoses observed in the rat under the in-fluenceof optimal conditions of stimulation is very similar to that formerly established in the case of the guinea pig'.
Associated with this increased proliferative activity of the acinar epithelium, there are observed the other structural changes in the thyroid gland indicative of increased metabolic activity, previously noted in the case of the guinea pig. The average index of mitotic proliferation which we found in the thyroid gland in the control rats is somewhat lower than that observed by Chouke. This may possibly be due to differences in the season of the year; however, this point needs further investigation.
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