VIII 



THE EXCEET10X OF I'lMXK 



447 



which records the variations of volume that take place in the 

 kidney. By the application of this method Eoy (1881) devised 

 an ingenious apparatus which he called the ona >///'</ />//, as shown 

 in Figs. 117, 118, 119. 



It is plain that the rapid variations of volume in the kidney 



FK-. 11$. Oncometer as in Pig. II 1 ! litted up for experiment (cross section : proper size). 



as in last figure. The dotted line // is a thin non-elastic membrane (calf's peritoneum'), the 

 edges of which are clamped in each half of the box between the two chambers. A and B, 

 the space between tin; membrane and the inner, lower chamber, is tilled with oil through the 

 opening, which is then closed by a tap F. The kidney >', is then placed on the membrane 

 raised by the oil, so that the whole of the nerves and vessels with the ureter (which enter the 

 hilum enclosed in a fatty sheath) pass out at the aperture K without being compressed. The 

 box is then closed, and tlm space between the two membranes and the inner chamber of the 

 upper half is also lilled with oil, through the tube e, which is closed by a tap. Every change 

 of volume in the kidney must now displace the oil, and is transmitted through the tube E to 

 the recording apparatus. 



can only depend on variations in its vascular circulation ; 

 dilatation of the renal vessels produces increase, constriction of 

 the vessels decrease, in the kidney volume. In oucographic 

 curves, as in kyniographic tracings from an artery, we can dis- 

 tinguish the oscillations of the sphygmic wave due to the cardiac 

 rhythm, the undulations of the second order due to the respiratory 

 rhythm, and occasionally the slower undulations of the third order 



