THE DUCTLESS GLANDS 413 



and the ease with which recovery takes place. Idiosyncrasy 

 plays a large part in the conditions. A partial immunity can 

 be set up by giving doses insufficient to kill (8). Subcutaneous 

 injections produce glycosuria in rabbits and dogs (9). The 

 substance probably acts as a protoplasmic poison (10). 



(d) Special physiological effects of extracts of the suprarenal 

 capsules; Effects of intravenous injections. — The most important 

 observation after that of Addison is the discovery of Oliver and 

 Schafer (11) in 1894 that extracts of the medulla of the capsules 

 when injected into the circulation of a living animal give rise 

 to an enormous rise of the blood-pressure, which is still greater 

 when the vagi are cut or atropine is administered. The effect 

 is a peripheral one. The flow of secretion from the salivary 

 glands is increased (12). Repeated injections of adrenin into 

 the auricular vein of the rabbit give rise to a degenerated 

 condition of the wall of the larger arteries, especially of the 

 aorta (arterio-sclerosis) (13). This effect is also produced by 

 other blood-pressure-raising substances, such as digitalin and 

 nicotine (14). 



(e) Mode and scat of action of suprarenal extracts. — According 

 to recent observations by Langley, in all cells two constituents 

 at least must be distinguished : (1) substances concerned with 

 carrying out the chief functions of the cells, such as contraction, 

 secretion, the formation of special metabolic products ; and (2) 

 receptive substances, especially liable to change, and capable 

 of setting the chief substance in action. According to this 

 author the active substance of the suprarenal capsules produces 

 its effects by combining with the receptive substance, and not 

 on nerve-endings nor the chief substance (15). So that in this 

 view the controversy as to whether adrenalin acts on muscle itself 

 or on sympathetic nerve-endings is compromised by assuming 

 that there is some material in cells originally under control of 

 the sympathetic which is specially excited by adrenalin. 



'(f) The chemical nature of the physiologically active substance. — 

 The active principle was first obtained in crystalline form by 

 Takamine and Aldrich independently. Takamine calls his 

 product adrenalin. It has the empirical formula C 9 H 13 N0 3 , and 

 the probable structural formula is : — 



HO 

 HO/ \CH (OH) . CH 2 NH CH, 



