i INTERNAL PROTECTIVE SECRETIONS 57 



entire morbid syndrome exhibited acutely after total destruction 

 of the capsules, depends on the depression of tone in the vasomotor, 

 cardiac, and respiratory centres, and also in all probability of the 

 centres of muscular tone. 



The active substances produced by the capsules (which reach 

 the blood by the suprarenal veins) thus serve to keep up the normal 

 tone of all these centres. 



This view is supported by a series of experiments carried out 

 partly with the collaboration of Szymonowicz, which may be 

 summarised as follows : 



(a) After complete extirpation of both capsules (which the dog 

 only survives for eight to fifteen hours) the arterial pressure falls 

 to 20 mm. Hg below the normal ; pulse and respiration become 

 considerably slower. Intravenous injection of aqueous supra- 

 renal extract raises pressure conspicuously, slows the pulse, and 

 quickens respiration ; while the injection of other organic extracts 

 has no effect. 



(&) After section of the cervical cord, injection of suprarenal 

 extract has no effect, showing that the increase of pressure is due 

 to excitation of the bulbar vasomotor centre. On cutting the vagi, 

 the slowing of the pulse caused by injection of the extract ceases, 

 showing it to be clue to stimulation of the moderator centres of 

 the heart. 



(c) The active substance is formed not after death, but during 

 the life of the suprarenal bodies, passing by diffusion into the 

 epithelial cells of the efferent veins. In fact, if the reduced venous 

 blood from the capsule is collected and defibrinated, and then 

 injected into the veins of an animal, the same phenomena are 

 produced as are seen after injection of suprarenal extract, though 

 less acutely. The venous blood from any other vein has no effect 

 in the same doses. These results were confirmed by Sal viol i and 

 Pezzolini (1902). 



(d) A long series of experiments shows that the active substance 

 formed by the suprarenals is not toxic in moderate doses, but 

 merely raises the tone of the vasomotor, respiratory, and cardiac 

 centres, as well as the centres for muscular tone. 



(e) The transitory nature of the excitation of the above centres 

 by the active substance manufactured by the capsule, is explained 

 on the assumption that it is partly eliminated by the kidneys, 

 partly transformed by oxidation within the tissues. Probably the 

 increase of arterial pressure, the slowing of the pulse, and the 

 dyspnoea that accompanies the asphyxia, depend on the accumu- 

 lation within the body of the active substances formed by the 

 capsule, which under normal conditions are destroyed as fast as 

 they form. 



The exact physiological action of suprarenal extract on various 

 tissues has been recently studied by Velich, Biedl, Wiesel, Gottlieb, 



