1. Mallory's connective tissue stain used in connection with fixation of tissue by Zenker's fluid or bichloride of mercury demonstrates the presence or absence of iodin in the thyroid colloid, as is evidenced by parallel chemical determinations, iodin feeding, and test-tube experiments.
2. Greatly increased activity of the heart is accompanied by a loss of thyro-iodin from the colloid of the thyroid.
3. This method, while apparently not adaptable to clinical use, may prove of value in further experimental work on the thyroid.