236 ORIGIN AND NATURE OF LIFE 



suprarenals. This disease shows a peculiar 

 bronzing of the skin occurring in patches, 

 and is accompanied by progressing muscular 

 weakness, listlessness, and eventually extreme 

 lassitude. It is invariably fatal. Next 

 Brown-Sequard showed that the removal of 

 these tiny glands always led to fatal results. 

 This was confirmed by Schafer and other 

 observers, and the clinical picture is that of 

 an excessively rapid Addison's disease. The 

 discovery was next made by Schafer and 

 Oliver, that these glands are constantly 

 supplying to the blood a chemical hormone 

 which possesses a tonic or stimulating action 

 upon the heart and arteries, particularly the 

 small arteries, or arterioles, leading to the 

 capillaries. The substance has since been 

 isolated, and is known as adrenalin. It has 

 even been prepared artificially, and its 

 chemical constitution is well known. When 

 even a minute amount is injected into a vein, 

 it exercises such a constricting effect upon the 

 muscular coats of the small arteries that the 

 bore is nearly obliterated, and as the heart 

 still goes on pumping with even greater force, 

 the pressure in the arteries may mount to 

 double or even treble its usual amount. 

 It is obviously the absence of this substance 

 in Addison's disease which gives rise to the 



