THE GLANDS: THYROID AND PITUITARY 49 



roid one has, the faster one lives; the less one has, the more slowly • 

 one lives. 



That is not to imply any direct proportion between the amount 

 of thyroid secretion in an individual, and the length of life to 

 which he is destined. The speed of living, in the chemical sense 

 (which is the fundamental s^nse), and the rate at which the 

 chemical reactions go on that constitute the process of life, are ** 

 dependent upon the thyroid. When the reactions go faster, more 

 oxygen and food material are burned up or oxidized, more energy 

 is liberated, the metabolic wheel rotates more quickly, the indi- 

 vidual senses, feels, thinks and acts more quickly. 



Likening one energy machine to another, the thyroid may be 

 compared to the accelerator of an automobile. That is a rough 

 and superficial comparison because an accelerator lets in more 

 of the fuel to be burned up, while the thyroid makes the fuel 

 more combustible. It thus resembles more the primer, for a rich 

 mixture of gasoline and air burns at a greater velocity than a 

 poor one. But the action of thyroid could really be simulated 

 only by some substance that could be introduced into the best 

 possible of gasoline mixtures, to increase its combustibility by a 

 hundred per cent or more. For that is what thyroid will do to 

 our food. Nor has it only this destructive or combustion side. 

 Withal there is at the same time a constructive action, for the 

 process frees energy to be used for heat, motion or other need. 

 The thyroid, therefore, in addition to its role as an accelerator, _ 

 acts, too, as the efficient lubricator for energy transformations."* 

 So we see it as accelerator, lubricator and transformer of ouil. 

 energies. 



The Gland of Energy Production 



The isolation of thyroxin has made possible the determination 

 of the influence of the thyroid hormone upon the evolution of 

 energy in any higher animal organism. There is, for every indi- 

 vidual, a constant, known as the metabolic rate, or the combus- 

 tion rate, a reading of the rate at which his cells are consuming 

 material for heat. The metabolic rate is thus a gauge of the 

 energy pressure within the organism. It may be calculated by 

 measuring the amount of carbon dioxide gas exhaled during a 

 unit of time, and the number of calories of heat radiated by the 

 skin simultaneously. A simplified device has lately rendered it 

 practicable to make actual determinations by a few five-minute 



