540 



THE URINARY APPARATUS. 



[CH. XXXVI. 



blood which causes the rise in the amount of urine secreted. If 

 the blood-pressure is increased without allowing the blood to flow 

 the amount of urine formed is not raised. This can be done by 

 ligaturing the renal vein ; the blood-pressure within the kidney 

 then rises enormously, but the flow of urine stops. 



Fig. 426. Oncometers for kidneys of different sizes. 



Another effect of ligaturing the blood-vessels of the kidney 

 must be here mentioned. If the vessels are temporarily ligatured, 

 and then the ligature is released, the urine which is then formed 

 is for a time albuminous. This is because the temporary anaemia 

 of the kidney produced by the ligature has lessened the vitality 



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Fig. 427. Curve taken by renal oncometer compared with that of ordinary blood- 

 pressure, a, Kidney curve ; b, blood-pressure curve. (Eoy.) 



of the renal epithelium in such a way that it is no longer able to 

 prevent the escape of albumin from the blood. 



The Oncometer is an instrument constructed on plethysmo- 

 graphic principles, by means of which the volume of the kidney 

 is registered. The general characters of this instrument are 

 described in the diagrams on pp. 310, 311. The special form 

 adapted for the kidney is shown in fig. 426. An air oncometer 



