18S1.] Mr Roy, On the mechanism of the renal secretion. Ill 



of inquiry were not however of a kind fitted to throw light upon 

 the problem which it was specially desired to solve. 



It soon became evident that an investigation of the manner in 

 which the renal secretion and circulation are normally regulated, 

 and the relation which these bear to the regulating mechanism of 

 the systemic circulation would be best fitted to supply information 

 of the kind required. 



The method employed was, to record graphically the changes 

 in volume of one or both kidneys, while at the same time the 

 changes in the blood-pressure in the aorta and the rapidity with 

 which the urine was secreted were also recorded on the same 

 revolving cylinder or, as continuous tracings, upon the paper of 

 Ludwigs kymograph. 



The method used for recording the changes in volume of the 

 kidney is the same in principle as that of the plethy sinograph. 

 The kidney is enclosed in a rigid metal box, the arrangement 

 being such that while the organ can freely expand or contract, and 

 while the changes in volume are recorded by a lever writing with 

 a light glass pen upon the kymograph paper, no obstruction is 

 offered to the entrance and exit of blood by the renal vessels nor 

 to the outflow of urine by the ureter. The kidney is surrounded 

 by warm olive oil, which, however, is not in immediate contact with 

 its surface, but is separated from it by a delicate flexible mem- 

 brane of a kind which has already been referred to by the author 

 in several of his published papers, and which prevents any escape 

 of the oil by the side of the blood-vessels and other structures 

 entering the hilus of the gland. It is impossible, consistently with 

 the brevity desirable in a communication of this kind, and without 

 the aid of a diagram, to describe in a satisfactory manner the exact 

 arrangement of the parts of the instrument, and the reader is referred 

 for the complete account of the method used to a paper which will 

 shortly be published in conjunction with Professor Colmheim giving 

 an account of the first part of these observations. At present it 

 must suffice to say that, when the instrument is in use, the kidney 

 lies between two delicate, exceedingly flexible membranes, which 

 apply themselves closely to its surface and to the surface of the 

 structures entering the hilus of the organ, and that each of these 

 membranes forms with each of the symmetrical halves of the box 

 a chamber which is filled with oil and which communicates by a 

 relatively wide flexible tube with the recording instrument. 



The metal box is roughly kidney-shaped, and the two symme- 

 trical halves, the edges of which meet in a plane corresponding to 

 the long axis and the hilus of the kidney, are joined together by a 

 hinge. Opposite the hinge each half of the box has a semicircular 

 incision cut into it, and these together form a round hole through 

 which pass the structures entering the hilus. 



