A SUGGESTION AS TO THE EFFECT OF THYROID GLAND SUBSTANCES ON PROTOPLASM IN GENERAL

¹ From the Department of Zoölogy, Oberlin College

1. Roots growing from bulbs of Narcissus into Pfeffer's nutrient solution to which has been added certain amounts of thyroid gland substance show a growth which is markedly abbreviated as compared with that of the control lines. This result is wholly like that when Allium is used.

2. Measurements directed to find out the internal conditions correlated with shorter growth indicate that differentiation of the special root tissues extends nearer to the tip of the root in thyroid "fed" lines than it does in the controls.

3. Assuming that the tissues in freshly growing plant roots can be compared to those in larval animals (Amphibia)—both originate from essentially unspecialized masses, although the plant never reaches the complexity of the animal—it would seem that thyroid substances cause precocious differentiation in both.

4. The suggestion is offered that animal and plant protoplasm are sufficiently, alike in their general physiology so that they respond similarly to thyroid substances; or, expressed conversely, thyroid substances are influential in essentially the same manner on all protoplasm.