METHODS. 



643 



selves with a measurement of the general blood pressure, and could only 

 obtain direct evidence as to the local changes in the renal circulation by 

 inspection of the kidney. It was not until the ingenious application of 

 plethysmographic methods to the kidney in situ, by Roy, 1 that we could 

 obtain a precise and quantitative estimate of the changes produced on the 

 circulation through this organ by the measures employed by the older observers. 



Roy's instrument for registering changes in the volume of the kidney 

 consists of two parts, in one of which, the oncometer, the kidney is placed, 

 while another, called the oncograph, serves as the recording part of the 

 apparatus. The oncometer consists of two halves hinged together, each of 

 which is formed of two metal capsules screwed together by the screw C, and 

 holding between them the membrane H. The two halves thus form a box. 

 When the two halves are ap- 

 proximated, the box is closed 

 except at one point K, opposite 

 the hinge, where there is an 

 opening to allow the passage of 

 the renal vessels and nerves, 

 and the ureter to the kidney, 

 which is placed within the box. 

 During use, the space between 

 the membrane and the metal 

 box is filled with warm oil 

 through the opening in the 

 screw. The opening in one-half 

 is then closed with a plug, 

 while the other communicates 

 by a tube E, with the onco- 

 graph. It is evident that any 

 change in the volume of the 

 kidney will be communicated 

 to the oil between the mem- 

 brane and the capsule, oil being FlG 6 1. Roy's oncograph. Diagrammatic section, 

 driven out into the tube t, The cylinder M is filled with oil, and corn- 



when the kidney swells, and municates by the tube K with the oncometer. 



being sucked in directly any Changes in the height of the oil are communi- 



u i 4-t. i j cated by the piston D to the lever H, the ex- 



shrmkmg of the kidney occurs. cursions of which serve therefore as an index of 



The oncograph, which is prac- the changes in volume of the kidney, 



tically a piston - recorder, in 



which the piston is made oil-tight by resting on a loose peritoneal membrane 

 tied round the tube, serves to register the amount of oil driven out or sucked 

 into the oncometer, and therefore at the same time the changes in the volume 

 of the kidney. 



A simpler and more efficacious form of oncometer, in which air instead of oil 

 is used, has been devised by Schafer 2 for the spleen, but is equally applicable 

 to the kidney. A description of it will be found in the section dealing with 

 the physiology of the circulation. 



Nerve supply. Before discussing the effects of various operative 

 procedures on the circulation of the kidney, it will be necessary to say a 

 few words concerning the nerve supply to this organ, since its vessels, 

 like those of all other parts of the body, are under the direct control of 

 the central nervous system. 



The gross distribution of nerves to the dog's kidney has been the 

 subject of a careful investigation by Nollner 3 in Eckhard's laboratory. 



1 Journ. PhysioL, Cambridge and London, vol. iii. p. 205. 2 Ibid., 1896, vol. xx. 



s Beitr. z. Anat. u. PhysioL (Eckhard), Giessen, 1869, Bd. iv. S. 139. 





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