METHODS. 
r >43 
' 
^ 
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 
plethysmography 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 i >pening 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 
driven out into the tube t, 
when the kidney swells, and 
being sucked in directly any 
shrinking of the kidney occurs. 
The oncograph, which is prac- 
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. 
Fig. 61. — Roy's oncograph. Diagrammatic section. 
The cylinder M is filled with oil, and com- 
municates by the tube K with the oncometer. 
Changes in the height of the oil are communi- 
cated hy the piston I) to the lever //, the ex- 
cursions of which serve therefore as an index of 
the changes in volume of the kidney. 
1 Joum. Physiol., Cambridge and London, vol. iii. p. 205. - Ibid. 
3 Beitr. z. Anat. u. Physiol. {Eckhard), Giessen, 1869, Bd. iv. S. 139. 
1896, vol. xx. 
