WHAT IS PHYSICAL LIFE 



suit. Hence we are always uncomfort- 

 able if these sympathetic nerves are irreg- 

 ular in their duty. Thus a sunstroke so 

 injures the sympathetic in the neck that 

 for years the patient's head and face flush 

 on the slightest provocation. Now these 

 vasomotor nerves lose all power to regu- 

 late the arteries if the adrenal glands are 

 out of commission. And the reason seems 

 to be this: That early in embryonic life 

 a twig of the renal (kidney) plexus of the 

 sympathetic becomes rolled on itself like 

 a ball of twine. In time it breaks off from 

 its parent stem, and, becoming enclosed 

 in a capsule, adheres to the top of the 

 kidney as a fully formed adrenal gland. 

 The marvellous thing then is that these 

 adrenals add an internal secretion to the 

 blood, which contains a definite chemical 

 substance which combines with acids and 

 forms salts, and is called adrenalin. This 

 adrenalin is virtually a drug, and as it 

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