THE THYKOID 2S 



A number of investigators among them the justly 

 famous Mayo brothers of Rochester showed that 

 where surgical removal of the thyroid becomes im- 

 perative, myxedema may be prevented by leaving 

 intact at least one-fourth of the organ. 



Iodine in the thyroid. It would have been 

 strange if no attempts had been made to isolate 

 the hormone or active principle present in the thy- 

 roid gland. As a matter of fact, many such at- 

 tempts were made, particularly after the success- 

 ful isolation of the active principle of the adrenal 

 glands. The first important discovery that was 

 made in this direction was by Baumann in 1895, 

 who showed that the thyroid is rich in the element 

 iodine. Until Baumann's time no one had had the 

 slightest suspicion that such an element as iodine 

 existed in the body; yet a careful analysis of the 

 thyroid showed it to be there in appreciable quan- 

 tity. That naturally suggested two things: that 

 the active principle of the gland was an iodine com- 

 pound, and that iodine, or more likely foods con- 

 taining iodine, have to be supplied to the body. 



Isolation of the thyroid hormone. Much work 

 has since been done on the chemistry of the iodine 

 compound in the gland. Various substances have 

 been isolated from it containing percentages of 

 iodine greater than that in the whole gland, show- 

 ing that the preparations, if not pure, did at least 

 represent concentrated fractions. These sub- 



