PARATHYROID GLANDS 13 



a dog with iodoform, the iodine content and the 

 activity of the thyroid colloid are both increased 

 greatly. The thyroid secretes into the blood, as 

 iodothyrin, the iodine derived from the iodoform. 

 When strychnine is excreted by the kidneys the 

 excretion is merely discharged from the body, and 

 therefore the drug can do no more harm. But the 

 increased secretion of the thyroid is discharged not 

 externally but into the blood, and may poison the 

 patient. 



ACTION OF IODIDES ON GUMMATA AND 

 ATHEROMA. 



A similar increase in the thyroid secretion may 

 be obtained by giving iodides, but apparently the 

 gland is not able to utilize these as readily as it does 

 iodoform, for large doses do not so easily cause 

 acute thyroid intoxication. Here we find the ex- 

 planation, so long sought in vain, of the effect of 

 iodides on gummata, arteriosclerosis, and aneurysm. 

 The beneficial agent is really the increased internal 

 secretion of the thyroid gland. 



Two important results of observation and experi- 

 ment confirm this theory. 



In the first place, in cases of myxoedema, arterio- 

 sclerosis is early and intense. The same is true in 

 animals after removal of the thyroid. Eiselsberg 

 gives a number of very convincing photographs of 

 intense atheroma of the aorta in his cretin lambs 

 in which the thyroid had been removed in early life. 

 In the second place, thyroid extract has a wonderful 

 power over young connective tissue, as is seen by the 



