EXPERIMENTS WITH THE ONCOMETER. 429 



oncograph (fig. 287), which is provided with a movable piston, p, attached by a 

 thread to the writing-lever, I. Any increase in the size of the organ expels oil 

 from the chamber, O, into C', and thus the piston is raised, while a diminution in 

 the size of the kidney diminishes the fluid in C, and the lever falls. The actual 

 volume of the living kidney depends upon the state of distension of its structural 

 elements, upon the amount of lymph in its lymph-spaces, but chiefly upon the 

 amount of blood in its blood-vessels, and this again must depend upon the condi- 

 tion of the non-striped muscles in the renal arteries. When the vessels dilate, the 

 kidney increases in size, and when they contract it contracts, so that we can 

 register on the same revolving cylinder the variations of the volume at the same 

 time that we record the general arterial blood-pressure.] 



[In the normal circulation through the kidney, the kidney curve, i.e., the curve 

 of the volume of the kidney, runs parallel with the blood-pressure curve, and shows 

 the large respiratory undulations, as well as the smaller elevations due to the systole 

 of the heart (fig. 288). Usually, when the blood-pressure falls, the kidney curve 

 sinks, and when the blood-pressure rises the volume of the kidney increases. 

 When the blood-pressure curve is complicated by Traube-Hering waves ( 85) the 

 opposite effect is produced on the kidney curve ; the highest blood-pressure corre- 

 sponds to the smallest size of the kidney, and conversely. This is due to the fact 

 that, when these curves occur, all the small arterioles, including those in the kidney, 

 are contracted. A kidney placed in an oncometer secretes urine like a kidney 

 under natural conditions.] 



E.r 



Fig. 288. 



B.P., Blood-pressure curve ; K., curve of the volume of the kidney ; T, time curve, intervals 



indicate a quarter of a minute ; A, abscissa (Stirling, after Hoy). 



[Arrest of the respiration in a curarised animal produces a rapid and great 

 diminution of the volume of the kidney, caused by the venous blood stimulating the 

 vaso-motor centres, and thus contracting the small arterioles, including those of the 

 kidney. This result occurs whether one or both splanchnics are divided, proving 

 that all the vaso-motor nerves of the kidney do not reach it through the splanch- 

 nics. When all the renal nerves at the hilum are divided, arrest of the respiration 

 causes dilatation of the organ, which condition runs parallel with the rise of the 

 blood-pressure. Stimulation of a sensory nerve, e.g., the central end of the sciatic 

 nerve, while causing an increase of the blood-pressure, makes the kidney shrink.] 



[In poisoning with strychnin, the kidney shrinks while the blood-pressure rises. 

 Stimulation of the central or peripheral end of the splanchnics, divided at the 

 diaphragm, causes contraction of the renal vessels" of both sides ; the former is a re- 

 flex, the latter a direct effect. Stimulation of the peripheral end of one splanchnic 

 sometimes affects both kidneys. Stimulation of the peripheral end of the renal 

 nerves always causes a diminution in the volume of the kidney, so that Cohnheini 

 and Roy inferred that, although there was evidence of the existence of vaso-motor 

 and sensory nerves to the kidney, they found none of vaso-dilators. Each kidney 

 acts independently of the other. Sudden compression of one rental artery has not 

 the slightest effect upon the blood-current of the other kidney. If a kidney be 



