4 88 A MANUAL OF PHYSIOLOGY 



the malady which now bears his name, and in which certain 

 vascular changes, with muscular weakness and pigmentation 

 or ' bronzing ' of the skin, are prominent symptoms, was 

 associated with disease of the suprarenals. This clinical 

 result was soon supplemented by the discovery that extirpa- 

 tion of the capsules in animals is incompatible with life 

 (Brown-Sequard). Our knowledge of the functions of 

 these hitherto enigmatic organs has been greatly extended 

 by the experiments of Oliver and Schafer, who have in- 

 vestigated the action of extracts of the suprarenals (of calf, 

 sheep, dog, guinea-pig and man) when injected into the 

 veins of animals. The arteries are greatly contracted, and 

 this mainly through direct action on the vaso-motor nerve- 

 endings or the smooth muscle of the vessels, but partly 

 through the vaso-motor centre. The blood-pressure rises 

 rapidly, although the heart is strongly inhibited through the 

 vagus centre. The heart is at the same time directly stimu- 

 lated, so that although it beats slowly, the beats are stronger 

 than before. When the vagi are cut the action of the heart 

 is markedly augmented, and the arterial pressure rises 

 enormously (to four or five times its original amount). 

 Stimulation of the depressor is of no avail in combating 

 this increase of blood-pressure. The vessels of the con- 

 junctiva are constricted by local action when an extract of 

 the capsules is dropped into the eye, a fact which has proved 

 of value in ophthalmological practice. The smooth muscular 

 fibres of the dilator pupillae and the retractor of the nictitating 

 membrane in the cat are stimulated by intravenous injection 

 of it after all the nerves going to them have been severed. The 

 curve of contraction of the skeletal muscles is lengthened 

 as in veratria poisoning (p. 570), though to a less extent. 

 The active principle that produces these effects is solely 

 contained in the medulla of the gland, and such is its 

 extraordinary power that a dose of one-millionth of a gramme 

 per kilo of body-weight is sufficient to cause a distinct 

 effect upon the heart and bloodvessels. It was entirely 

 absent from the suprarenals of a person who had died of 

 Addison's disease. Abel has isolated as a benzoyl compound 

 the substance which causes the rise of blood-pressure. He 



