DUCTLESS GLANDS — TAYLOR 703 



be seen, he is a sad reproach to some one, whether physician or parent, 

 who has failed to bring to this blighted one the certain cure which 

 is ready at hand. 



There is another reason why cretins are rare to-day, and that is 

 the occurrence of goiter is prevented. The cause is removed. Iodine 

 is added to the drinking water or the food, or given in small doses 

 a few times a year to the children of the Swiss cantons and other 

 regions where goiter is prevalent. 



There is little doubt, then, of one function of the thyroid gland. 

 It controls the growth and the development of both body and mind. 

 It takes iodine and other materials from the blood and manufactures 

 a secretion or hormone which produces these effects. 



In order to bring further conviction, I shall cite a very interesting 

 experiment that was carried out a few years ago upon tadpoles, 

 ordinary polliwogs, whose destiny is, as you know, to grow into frogs. 



A group of tadpoles which had been hatched from the same batch 

 of eggs a short time previously was placed in a small aquarium. 

 A number of these creatures were operated upon and their thyroids 

 removed — rather small subjects, you might think, for a major opera- 

 tion, and rather poor risks, too. But a certain proportion of them 

 made a good recovery and continued to swim about after their con- 

 valescence, just like a number of their brothers who had been allowed 

 to keep their thyroids. 



The animals without thyroids, however, never grew into frogs. 

 The experimenter, with his scalpel, had shaped their destinies. 

 The joys of frogdom were not for them. Never were they to spring 

 from slimy pools to breathe the air or bask in sunshine upon a lily 

 pad. They remained polliwogs for the rest of their lives. They 

 were the counterparts of human cretins in so far as body growth 

 and development went. Since their mentality is scarcely of a meas- 

 urable quantity, no one can say how they progressed in that direc- 

 tion. They can not be subjected to intelligence tests, nor do we 

 know what their brothers thought of them ; so that side of the ques- 

 tion must be left to the imagination. Their normal brothers, which 

 were kept under precisely the same conditions, lost their gills and 

 tails, grew arms and legs, and matured into frogs in the usual way 

 and in the usual length of time, two and a half to three months. 



If thyroid extract was given to the cretinoid tadpoles — a small 

 quantity merely dropped into the water in which they swam, or fresh 

 thyroid tissue fed to them — they commenced to develop in the usual 

 way and in due time were hopping about, perfectly normal frogs. 



On the other hand, when extract was added to the water in which 

 the normal tadpoles lived, those which were not deprived of their 

 thyroids — they developed into frogs ahead of time. Their develop- 

 ment was speeded up. The gills and tail disappeared and the limbs 



