NORMAL AND PATHOLOGICAL GROWTH 153 



gland as on the greater rate of functional activity. This hor- 

 mone is an iodin compound of an amino acid. It was chemically 

 isolated and identified by Kendall 5 in 19 15, who named the 



Figure 78. Typical appearance of untreated cretin, 

 hypothyroidism of infancy. From Diseases of Infancy 

 and Childhood by Drs. Holt and Howland. Courtesy of 

 D. Appleton and Company, New York. 



substance thyroxin. It contains as much as 63 per cent of iodin. 

 Harington 6 has recently determined the correct clinical formula 



T I 



as HO 



V 



CH, CH(NH 2 ) COOH. 



I I 



The thyroid hormone accomplishes its accelerating influence 

 on physiological processes through direct stimulating action on 



