EXCRETION 409 



The Influence of the Circulation on the Secretion of Urine. 

 Although the activity of no organ in the body is governed 

 more by the indirect effects of nervous action than that of 

 the kidne)', no proof has yet been given of the existence of 

 secretory fibres for it comparable to those of the salivary 

 glands. All the changes in the rate of renal secretion which 



B, metal box in 

 two halves opening 

 on the hinge H ; 

 M, thin membrane ; 

 A, space filled with 

 oil ; O, organ en- 

 closed in onco- 

 meter ; V, vessels of 

 organ ; t, tube for 

 filling instrument 

 with oil ; T, tube 

 connected with D, 

 which opens into 

 cylinder C ; C is 

 also filled with oil; 

 P, piston attached 

 by E to a writing 

 lever. 



FIG. 128. DIAGRAM OF ORGAN -PLETHYSMOGRAPH OR ONCOMETER. 



follow the section or stimulation of nerves can be explained 

 as the consequences of the rise or fall of local or general 

 blood-pressure, and of the corresponding variations in the 

 velocity of the blood in the renal vessels. 



The best way to study variations in the calibre of the renal vessels 

 is the plethysmographic method, and the oncometer of Roy is a 

 plethysmograph adapted to the kidney. It consists of a metal 

 capsule lined with a loose membrane, between which and the metal 

 there is a space filled with oil. The two halves of the capsule open 

 and shut on a hinge ; and the kidney, when introduced into it, is 

 surrounded on all sides by the membrane, the vessels and ureter 

 passing out through an opening. The oil-space is connected with a 

 cylinder also filled with oil, above which a piston, attached to a lever, 

 moves. The lever registers on a drum the changes in the volume of 

 the kidney, i.e., practically the changes in the quantity of blood in it, 

 and therefore in the calibre of its vessels. A still better oncometer 

 is that of Schafer, in which air is employed instead of oil. 



Nerves of the Kidney. Both vaso-constrictor and vaso-dilator 

 fibres for the renal vessels, but most clearly the former, have been 

 shown to leave the cord (in the dog) by the anterior roots of the sixth 

 thoracic to second lumbar nerves, and especially of the last three 

 thoracic. They run in the splanchnics, and then through the renal 

 plexus around the renal artery into the kidney. The vaso- 

 constrictors predominate, so that the general effect of stimulation of 



