430 PHYSIOLOGY CHAP. 



obtained on making an artificial circulation through the vessels of 

 a kidney recently excised from the animal (I. Munk). 



It is accordingly rate of circulation rather than pressure which 

 governs the phenomenon of renal secretion. On the velocity of 

 the blood-flow depends not only the amount of excretory material, 

 but also the provision of oxygen required by the secretory cells 

 for their task. In proof of this we have the fact that when the 

 integrity of the living cells of the capsular epithelium of the 

 glomerulus is damaged, their function ceases at once, either for a 

 time or permanently. 



If, after a brief occlusion of the renal arteries, the renal circula- 

 tion is reinstated by opening the vessels, secretion is not resumed 

 at once, but after a certain lapse of time, which may vary from a 

 few minutes to three quarters of an hour. This phenomenon, 

 first observed by Max Herrmann in Ludwig's laboratory in 1859, 

 is not adequately explained by the theory which regards the 

 glomerulus as a passive filter, but is readily explained on the 

 assumption that the secreting epithelia of the glomerulus are 

 highly sensitive even to a temporary deprivation of oxygen, and 

 require a certain time to recover from the effects of asphyxia. 



Overbeck's experiments (1863) confirm this hypothesis. He 

 observed that after occlusion of the renal artery, lasting only for 

 one and a half minutes, the secretion came back slowly after 

 forty-five minutes; that the first urine collected was scanty in 

 amount, and contained much protein ; that the quantity of urine 

 subsequently increased, while the protein content diminished; 

 that, lastly, the urine gradually regained its normal constitution. 

 Herrmann endeavoured to explain the arrest of the urinary secre- 

 tion on the hypothesis that the suspension of circulation produces 

 such an accumulation of blood corpuscles in the capillary network 

 of the kidney as to block the renal circulation ; but this hypothesis 

 was contradicted by Litten, who proved that even after prolonged 

 occlusion of the artery the renal circulation remained normally 

 pervious. 



We hold the only acceptable interpretation to be that the 

 asphyxia of the living cells of the glomerulus alters them so as to 

 render them at first impermeable, and then at a second period, 

 after the circulation has been restored, abnormally permeable (even 

 to colloid substances). The fact that temporary albuminuria can 

 also be produced by suffocation, by strychnine poisoning, and 

 lastly by temporary obturation of the right heart (Overbeck), 

 agrees with this interpretation. 



That velocity of the blood-flow rather than pressure is the 

 determining factor in the formation of urine is a fact of the 

 utmost importance to the theory of urinary secretion. Murri was 

 the first to put forward this idea in Italy, in his clinical lectures 

 on Haemoglobinuria a frigore, published 1879, as a rejoinder to 



