1881.] Mr Roy, On the mechanism of the renal secretion. 113 



2. The renal vessels are exceedingly elastic, a rise or fall of 

 the aortic blood-pressure causing an expansion or contraction of 

 the kidney which may be very considerable in amount, e.g. in one 

 case a rise of the blood-pressure from 70 to 180 mm. of mercury 

 (brought about by closing the innominate and carotid arteries and 

 clamping the aorta below the point at which the renal arteries are 

 given off) caused an expansion of the kidney which was equal to 

 10 per cent, of the volume which the organ was found to measure 

 after death. 



3. The changes in volume of the two kidneys are not 

 necessarily identical either in quantity or in direction — one kidney, 

 for example, may be slowly expanding while the other remains 

 constant in volume or is even slowly contracting ; further, any 

 influence which causes contraction or expansion of the renal 

 vessels need not cause expansion or the opposite to an equal 

 extent in both glands. 



4. After the immediate effect of the operation has passed 

 off, the volume of the kidney will usually remain unchanged (with 

 exception of the changes due to the pulse and respiration) for 

 many hours unless some change in the conditions of the experi- 

 ment be intentionally introduced. 



5. When the Traube-Hering curves of the blood-pressure 

 present themselves, the volume of the kidney does not expand 

 with the rhythmic rise in the blood-pressure. With each rise of 

 the blood-pressure the kidney contracts, expanding with each fall 

 of the blood-pressure. The renal vessels are, therefore, amongst 

 those to the rhythmic contraction and expansion of which the 

 Travbe-Hering waves are due. 



6. Arrest for 3 or 4 minutes of the artificial respiration, where 

 that is employed, and where curare has been previously injected, 

 causes a contraction of the renal vessels (which may reach 12 per 

 cent, of the post-mortem volume of the kidney) simultaneously 

 with the rise of aortic blood-pressure which is produced by the 

 asphyxia. 



7. Stimulation of the medulla oblongata by weak induced 

 currents causes a powerful contraction of the renal vessels. 



8. Stimulation of the central end of a sensory nerve, e.g. sciatic, 

 brachial plexus, splanchnic, &c. causes a contraction of the renal 

 vessels simultaneous with the rise in the aortic blood-pressure. 



Stimulation of the central end of the vagus causes a con- 

 traction of the kidney (where the vagus of the other side has been 

 cut to eliminate reflex inhibition of the heart), and the renal 

 vessels contract whether the stimulation of the central end of 

 the vagus cause a rise or a fall of the aortic blood-pressure. 



VOL. IV. PT. II. 8 



