50 THE GLANDS REGULATING PERSONALITY 



readings of the rate of oxygen absorption by the lungs. Plummer, 

 also connected with the Mayo Foundation, has shown that what 

 would amount to less than a grain of the thyroxin would more 

 than double the amount of energy produced in a unit of time. 



m To be exact, one milligram of thyroxin increases the metabolic 

 rate two per cent. That illustrates some of the power of the 

 internal secretion of the thyroid and its importance to normal 



' life. 



The Mobilization of Energy 



But not only is the height of pressure of energy in the cells 

 controlled by the thyroid. The mobility of that energy is also 

 controlled. Without it, rapid and large fluctuations of energy 

 output, and elasticity and flexibility of energy mobilization for 

 any sudden mental or muscular act, let alone an emergency, be- 

 come impossible. A woman suffering with myxedema, the con- 

 dition described by the English physician Gull as a cretinoid 

 state supervening in the adult life of woman, has an insufficient 



""amount of thyroxin in her blood and tissues. She is clumsy 

 and awkward and will stumble when endeavoring to walk up- 



stairs. Any effort is almost paralyzed because the range of 



fluctuation of energy, the ability to mobilize energy, in turn de- 

 pendent upon an ability to increase the metabolic rate, is limited. 

 In slang phrase, she cannot step on it. Her existence is set to go 

 at a rate in the neighborhood of forty per cent below the normal. 

 By the administration of thyroxin, her metabolic rate can be 

 raised to any desired figure, the spark can be adjusted, so to 

 speak, to any point we like, and it can be so maintained for 

 years. 



In the normal animal, to be sure, the internal secretion of 

 the thyroid is not absolutely essential to life. So it contrasts 

 with the hormone of the minute parathyroids placed so closely to 

 it, a minimum dose of which is absolutely a prerequisite for con- 

 tinued life. The fundamental chemical reactions within the cells 

 occur in the complete absense of thyroxin. But they go on in 

 a relatively fixed, rigid and unvarying way, confined within the 

 narrow limits of a constant figure. Under such conditions, the 

 level of energy production is bound to be low, and to remain low, 

 and the modus of its mobilization slow and unwieldy. With 

 thyroid is introduced the trick of catalysis, or the speeding up of 

 the vital chemical reactions, through the agency of an intermedin 



