Abstract
Experiments were carried out on the parafollicular cells (PC) in the rat thyroid, with the following results.
These are independent cells which develop from follicular epithelium at 3 weeks of age, increasing with age. They can be divided into the clear and granular cells, and the transformation from one type to the other is noted. PC are independent from the changes produced in follicular epithelium by the administration of TSH, methylthiouracil or thyroxine.
PC are visible at long time after the hypophysectomy, becoming rather more distinct with the lapse of time. Any observable change was not induced by the administration of autnomic drugs nor by exposure to high or low temperature. PC did not take trypan blue in an attempt of vital staining.
From these results PC are considered to participate in the production of new follicles.
