442 INTERNAL SECRETION 



in a manner precisely similar, perish at the end of thirty-six hours. 

 In the second place, the appearance and course of the clinical 

 symptoms of uraemia is not, in such animals as these, a reliable 

 criterion of the condition. Many animals from which the kidneys 

 have been removed show no symptoms for two, three, or four 

 days, and then die, either suddenly or within a few hours, without 

 having shown any characteristic signs. In the case of other 

 animals, there is repeated vomiting and dyspnoea as early as the 

 first day after operation ; recovery is frequent, or there may be a 

 condition of chronic uraemia lasting for several days. Given 

 such conditions, I hardly think it possible to estimate the results 

 of any therapeutic measures at their proper value. Moreover, to 

 base a so-called physiological treatment of uraemia upon the 

 results of such experiments, and to apply this treatment, by the 

 exhibition of renal extract, to clinical nephritis, in my opinion, 

 shows a grave lack of judgment. 



Attempts have been made to prove the elaboration of an 

 internal secretion by the kidneys by means of renal extract. Oliver 

 and Schafer proved that the kidney belongs to that class of organs 

 the extract of which, when injected into the veins, invariably 

 produces an increase in arterial tension. Tigerstedt and Berg- 

 mann next showed (1898) that a substance is obtainable with 

 cold water from the fresh kidney which, when injected into the 

 veins of rabbits, produces within a comparatively short time a 

 more or less marked rise in blood-pressure. This active substance, 

 to which the name of " renin " was given by the discoverers, is 

 derived from the cortex, and, in very small quantities, from the 

 medulla; it is not dialyzable, it is soluble in water, in dilute saline 

 solution, and in glycerine; it is insoluble in absolute and in 50 

 per cent, alcohol ; it withstands heat up to 54 to 56, but is des- 

 troyed by heating in a water baih and by boiling. A rise in 

 blood-pressure is produced by this substance in very small 

 quantities, and is due to the effect which it has upon the peripheral 

 vessels, upon the nerve terminals, and perhaps also upon the 

 muscles. From the results of two experiments, Tigerstedt and 

 Bergmann assume that, under normal conditions, renin is con- 

 veyed into the blood which circulates through the kidneys. In 

 these experiments, blood from the renal veins was injected in 

 quantities of 2 c.cm. into the veins of rabbits which had been 

 nephrectomized one to two days previously, and a rise in blood- 

 pressure of 13 to 25 per cent, followed. These experiments were 

 afterwards tested by Lewandowsky, who found that the results 

 produced with 5 to 6 c.cm. of renal venous blood were in no way 

 different from those produced by the same amount of venous blood 

 from other parts of the body ; for this reason he is not prepared 

 to ascribe a specific vaso-contractor action to the blood in the renal 

 veins. 



The effect which renal extract has in raising blood-pressure 



