214 HEREDITY AND EUGENICS 



morphogenetic and affects the development, the other 

 which controls and regulates in a remarkable manner 

 various activities of the body through the minute 

 traces of certain substances which it pours into the 

 blood. This latter substance in the case of th3'roid 

 is known as thyroxin. It has been isolated and its 

 chemical structure determined, the molecule being 

 found to contain iodine and arsenic. About 150 

 grains were obtained from some 6,000 pounds of ox 

 thyroid, so that the amount of thyroxin poured daih' 

 into the blood of a man must be almost too infini- 

 tesimal for computation. The condition known as 

 myxcedema, which is accompanied by peculiarities of 

 the skin and hair, disappears when thyroid extract 

 is administered. Berman (1921) cites the fact that, 

 as early as 1891, sheep th3^roid was administered to a 

 woman with myxcedema.* The symptoms disap- 

 peared, but she was obliged to continue taking thyroid 

 extract until her death, in 191 9. In this period of 

 twenty-eight years she consumed nine pints of 

 thyroid, equivalent to the extract from the glands 

 of 870 sheep. 



Hence, the thyroid acts directly on the skin and 

 hair, which are the chief structures used in the classi- 

 fication of the races of mankind. It also affects the 

 skeleton, and when deficient, causes, according to 

 Keith, arrested development of the basal part of the 

 skull, the root of the nose appearing to be flattened 

 and drawn backw^ards between the eyes, the upper 

 forehead projecting or bulging, the face being flattened, 

 and the bony scaffolding of the nose greatly reduced. 

 These are all characteristic features of the Mongohan 



* A condition with dropsy-like swelling caused by failure of 

 nutrition from defective nerve influence. It is associated with 

 atrophy of the thyroid, and is probably directly due to excess 

 of mucin in the system. It is accompanied by sluggish move- 

 ments, thick speech, and dull mental condition. 



