378 HANDBOOK OF PHYSIOLOGY. 



more than one-third of the quantity excreted during the hours of diges- 

 tion." The increased amount of urine passed after drinking large 

 quantities of fluid probably depends upon the diluted condition of the 

 blood thereby induced. 



FIG. 261. Roy's Oncograph, or apparatus for recording alterations in the volume of the kidney, 

 etc., as shown by the oncometer a, upright, supporting recording lever I, which is raised or lowered 

 by needle 6, which works through /, and which is attached to the piston e, working in the cham- 

 ber d, with which the tube from the oncometer communicates. The oil is prevented from being 

 squeezed out as the piston descends by a membrane, which is clamped between the ring-shape? 

 surfaces of cylinder by the screw t working upwards; the tube h is for filling the instrument. 



The following table l will help to explain the dependence of the ni- 

 tration function upon the blood-pressure and the nervous system: 



TABLE OF THE RELATION OF THE SECRETION OF URINE TO ARTERIAL 



PRESSURE. 



A. Secretion of urine may be increased 



a. By increasing the general Hood-pressure; by 



1. Increase of the force or frequency of heart-beat. 



2. Constriction of the small arteries of areas other than that 



of the kidney. 



&. By increasing the local blood-pressure, by relaxation of the renal 

 artery, without compensating relaxation elsewhere; by 



1. Division of the renal nerves (causing polyuria). 



2. Division of the renal nerves and stimulation of the cord, 



below the medulla (causing greater polyuria). 



3. Division of the splanchnic nerves; but the polyuria pro- 



duced is less than in 1 or 2, as these nerves are distrib- 

 uted to a wider area, and the dilatation of the renal 

 artery is accompanied by dilatation of other vessels, and 

 therefore with a somewhat diminished general blood- 

 supply. 



4. Puncture of the floor of fourth ventricle or mechanical 



irritation of the superior cervical ganglion of the sympa- 

 thetic, possibly from the production of dilatation of the 

 renal arteries. 



1 Modified from M. Foster. 



