THE GLANDS: THYROID AND PITUITARY 51 



ate which accelerates the process. It is par excellence the great 

 catalyst of energy in the body. (A catalyst is an intermediary 

 like the trace of water, which will bring about an explosion be- 

 tween dry oxygen and hydrogen that without it have stayed 

 inert with the strongest currents of electricity.) Thus it supplies 

 a mechanism not only for quantity output of that subtle reality 

 we label energy, but also an apparatus for varying the available 

 amount of it, and for permitting the maximum range in ease and 

 rapidity of its utilization. The thyroid is still another device of 

 life for procuring more and more variation and differentiation, its 

 goal, as far as we can peer through the opalescent screen upon 

 which its manifestations quiver. 



From another point of view, the thyroid may be looked upon 

 as the organ evolved for maintaining the same amount of iodine 

 in the blood as there is in sea water. Sea water was our original 

 habitat, since, like Venus, we have all come up out of the sea. 



The more intimate study of the composition of the blood has 

 revealed the most astonishing parallelism between it and the 

 compounds of sea water. The blood is sea water, to which has 

 been added hemoglobin as a pigment for carrying oxygen to 

 the cells not in direct contact with the atmosphere, nutrients to 

 take the place of the prey our marine ancestors gobbled up 

 frankly and directly, and white cells to act as the first line of 

 defense. To keep the concentration of iodine in the blood a con- 

 stant, the thyroid evolved, since there is no iodine in most foods 

 and very little in those which do contain it. 



That a minimum amount of iodine in the food is necessary to 

 health is shown by the existence of goitre regions. Around some 

 of the Great Lakes in the United States, for instance, the water 

 does not contain enough iodine. As a result, numerous cases of 

 goitre occur. Iodine in the form of sodium iodide in small doses 

 will act as a prophylactic. The amount of iodine in the blood is 

 about one or two parts to ten millions, and that of the liver is 

 about three or four parts to ten millions. Since the liver is the 

 most complex and active chemical factory in the body, its 

 appropriation of a greater amount of iodine for itself is under- 

 standable. 



When thyroxin is administered in a single dose, there is a dis- 

 tinct lag in the absorption of it by the tissues. A single dose does 

 not generate its maximum effect until the tenth day. This effect 

 continues for about ten days. Then there is a gradual decrease 

 in the intensity of reaction for another ten days. So that the 



