CHAP, iv.] 



RENAL SECRETION. 



399 



them the edge of the membrane M which applies itself to the surface of the kidney, 

 and forms with the metal capsule two chambers a and B, one of which (B) is closed 

 by a plug filling the opening B, while the other (a) communicates by a tube T with 

 the recording instrument. The other opening C (which is closed by a small tap) is 

 for the purpose of filling the chamber a with warm oil, after the kidney has been 

 placed in the box, the other chamber B having been previously partly filled, the 

 quantity introduced into it depending upon the size of the kidney. 



FIG. 64. SEMI-DIAGRAMMATIC SECTIONAL VIEW OF ONCOGBAPH. Half natural size. 

 K tube connecting instrument with oncometer. D piston floating on oil contained 

 in the cavity M ; the oil is prevented from escaping by the side of the piston, by the 

 delicate flexible membrane E, which does not interfere with the movements of the 

 piston. H, recording lever connected with the piston by a needle G passing through 

 the guides F, F*. The screw C is for the purpose of clamping the edge of the membrane 

 between the two ring-shaped surfaces at N, while the side tube L is for the purpose 

 of filling the instrument. 



The instrument consists of two parts, one of which (Fig. 63) called 

 by Dr C. S. Roy, who introduced it, an oncometer l t is applied to the 

 organ about to be studied, while the other (Fig. 64), called the 

 oncograph, is the recording part of the apparatus. Any diminution 

 in the volume of the organ (Fig. 63, K), kidney, spleen, &c. as the case 

 may be, causes a diminution of the quantity of fluid in the 

 chamber a; this is transmitted through the tube T, continuous 

 with the tube K (Fig. 64) to the chamber M ; the piston D accordingly 

 falls and with it the lever H. Similarly an increase in the volume of 

 the organ causes the lever to rise. 



The volume of the kidney may be increased by a swelling of its 

 constituent cells and other structural elements, by an accumulation 

 of lymph in its lymph spaces and by a distension of its blood- 

 vessels. Compared with the third, the two former causes are in 

 health so insignificant and problematical that they may be disre- 

 garded. Further the distension of the blood-vessels will in general 



1 From oncos, bulk. 



