642 
THE SECRETION OE URINE. 
arteries. The pressure in the glomerular capillaries will be raised and 
the velocity of the blood increased- — 
1. By a rise of general blood pressure. This may be due to — 
(a) Increased force or frequency of the heart beat ; 
(b) Constriction of vascular areas in other parts of the body. 
2. By dilatation of the renal arterioles, the general blood pressure 
remaining constant. 
3. By obstruction of the renal vein. In this case the velocity will 
lie diminished. 
Fig. 60. — Diagrammatic section through Roy's oncometer, to show position 
of kidney. A, outer, and B, inner, brass capsules. These are fixed 
together by the screw C. G, the kidney. D, a clamp for fastening 
the two halves together after the kidney has been inserted. K, renal 
vessels and ureter. 
The pressure and velocity in the glomerular capillaries will be 
diminished — 
1. By diminished general blood pressure, which may arise from 
a weakening or slowing of the heart-beat, or from dilatation of vascular 
areas in other parts of the body. 
2. By constriction of the vessels in the kidney itself. 
Methods. — In the earlier researches 1 on the connection between the 
renal circulation and the flow of the urine, the observers had to content them- 
1 Max Hermann, Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1859, Bd. xxxvi. S. 349 ; 
1861, Bd. xlv. S. 317 ; Ustimowitsch, Arb. a. d. physiol. And. zu Leipzig, 1870. 
