278 MAN --AN ADAPTIVE MECHANISM 



more, we found that intravenous injection of placental 

 extract caused an increased output of adrenin in the 

 mother rabbit. In addition, we have shown in our 

 laboratory that histologic changes in the adrenals are 

 produced during normal pregnancy in cats and rabbits. 

 This evidence would seem to indicate that during preg- 

 nancy the adrenal link in the kinetic system performs 

 more than its normal amount of work. 



Thyroid: The thyroid enlarges during the mating 

 season. It enlarges during courting and mating ; in 

 most women, the thyroid undergoes some enlargement 

 during pregnancy. This enlargement may disappear 

 at the termination of pregnancy, and the gland return 

 to its normal condition. But in many instances a part 

 of the enlargement persists, and is increased with each 

 succeeding pregnancy, resulting finally in a large goiter. 



That this enlargement is a work phenomenon is 

 evidenced by the facts that in pregnancy the thyroid 

 not only is enlarged but becomes more vascular and that 

 two goiters excised during pregnancy from patients hav- 

 ing no symptoms of Graves' disease and no infection, 

 showed typical glandular hyperplasia. No other cases 

 of such typical glandular hyperplasia have been found, 

 excepting in patients whose kinetic systems were known 

 to be activated, as, for instance, in Graves' disease, 

 chronic pyogenic infection or tuberculosis. There is 

 additional evidence, moreover, that the thyroid is 

 hyperactivated in pregnancy. The pregnant woman 

 has the symptoms of mild Graves' disease, excessive 

 thyroid feeding or excessive administration of iodin, 

 namely : excitability, tremors, exhaustion, sleepless- 

 ness, increased metabolism, increased heart beat, 



