112 Mr Roy, On the mechanism of the renal secretion. [May 23, 



The recording instrument proper resembles in many respects 

 an arrangement which was described by the author in a paper 

 which appeared recently in the Journal of Physiology upon the 

 form of the pulse-wave. 



It need not be described here, and it must suffice to mention 

 that this instrument permits of even rapid changes in the volume 

 of the kidney being recorded without its producing the slightest 

 change in the pressure of the fluid by which the kidney is sur- 

 rounded. It allows also the numerical value of changes in volume 

 being ascertained with exactness. 



The rapidity of the flow of urine is followed with great con- 

 venience and accuracy by an arrangement by which each drop of 

 urine, which flows from a narrow tube tied in the ureter, falling 

 upon a light aluminium plate at the end of a well balanced lever, 

 causes, by its impact, a momentary descent of the latter, which dips 

 the point of a fine platinum wire into a mercury cup, closing 

 thereby for an instant a galvanic current, and causing a mark to 

 be made upon the paper of the kymograph by means of an electro- 

 magnetic marker. 



Each tracing then shews, 1st. the changes in volume of the 

 kidney, 2nd. the aortic blood-pressure, 3rd. the rapidity with which 

 the urine is being secreted, 4th. the time (which was recorded by 

 a seconds pendulum and an electro-magnetic marker in the 

 ordinary way). 



The operation is the same as that for nephrotomy, the kidney 

 being reached from the lumbar aspect. It is cleared of all its con- 

 nections leaving only intact the structures entering its hilus. It 

 is then enclosed in the metal box which has previously been 

 warmed, and the two compartments of which are now filled with 

 warm olive oil which fills also the flexible tube connecting the box 

 with the recording instrument. It need scarcely be added that 

 the animal, — rabbit, cat or dog, in most cases the latter, was kept 

 fully under the influence of ether, chloroform or morphia, or a 

 combination of two of these, from the commencement to the end 

 of the experiment. 



Contrary to what might reasonably have been anticipated, the 

 kidney continues to secrete urine of normal quality and in quantity 

 more or less exactly the same as that of the intact organ of the 

 other side, for many hours after it has been placed in the metal box. 



The following brief and incomplete resume may serve to 

 indicate the nature of the principal facts arrived at by Professor 

 Cohnheim and the author in Leipzig, or by the author inde- 

 pendently in Dr M. Foster's laboratory. 



1. The volume of the kidney varies with each pulse- wave and 

 with the respiration curves of the blood-pressure; — the tracing 

 obtained resembling closely that of the mercurial kymograph. 



