60 THE GLANDS REGULATING PERSONALITY 



sesame to certain long closed doors of biology. They offer them- 

 selves to us as the first definitely tangible agents which are 

 known to keep the process of growth going, and undoubtedly 

 initiate the marvelous unfolding of tissues and functions, organs 

 and faculties summed up as development or differentiation. 



Thus by the direct feeding of thyroid at particular points in 

 the differentiating history most curious effects have been elicited. 

 If the gland is made part of the nutriment, the bathing environ- 

 ment, of the tadpole, a hastening of its metamorphosis is attained. 

 The tadpole lives not out its day as a tadpole, but precociously 

 turns into a frog. But such a frog! It is a miniature frog, a 

 dwarf frog, a frog seen by looking through the wrong end of the 

 telescope, a frog not magnified, but micrified. Frogs have been 

 so created the size of flies. There has occurred a splitting of the 

 two reactions which ordinarily go hand in hand: the reaction of 

 growth which is just brute increase of total mass or weight and 

 volume, and the reaction of differentiation which is the finer 

 process. The picture is a frog, but a frog the size of a tadpole, 

 a frog which has missed its childhood, adolescence and youth, 

 skipping over these transition stages into the adult age, as a 

 pigmy. 



It is all as if a baby were suddenly to grow a beard and 

 moustache, evolve and shed teeth, and acquire the manner of an 

 earnest citizen, and yet retain the height and weight of a baby. 

 That the spectacle of such a superbaby is not quite the most fan- 

 tastic of all improbabilities is shown by the condition of progeria, 

 first recorded by the Briton, Hastings Guilford. A queer spec- 

 tacle in which a child incontinently grows old without having 

 lived — in the course of a few weeks or months. You look upon 

 him and see senility on a small scale, but with all its peculiari- 

 ties: wrinkled skin, apathy, gray hair and all the rest of it. 

 All we can say about it is that it is probably due to a paralysis 

 of all the glands of internal secretion, a removal of their influence 

 upon the cells. Contrariwise to the feeding of thyroid, removal 

 of the thyroid of tadpoles will prevent their development into 

 frogs. If iodine is then fed to them, say mixed with flour, normal 

 metamorphosis will occur. If Body is the tool chest which we 

 carry about with us, as Samuel Butler said, then to the thyroid 

 belongs the name of tool-maker. 



Another function of thyroid that must be taken into considera- 

 tion is what has been spoken of as its antitoxic function — in 



