THE RENAL CIRCULATION. 



159 



least. It is noteworthy that the dilated pulmonary vessels recover their original 

 calibre very slowly. 



Whether the dilatation of the locomotor organs be active or passive 

 is of no particular importance. The fact remains that the splanchnic 

 area forms the resistance box of the circulation, and when the splanchnic 

 vessels are contracted, the blood is driven with increased velocity 

 through the locomotor organs, and is 

 determined from the deep to the super- 

 ficial parts of the body. 



The Renal Circulation. 



The circulation in the kidney is 

 studied with great ease by the plethys- 

 mographies method. Cohnheim and 

 Hoy x constructed a metal oncometer 

 for this purpose. A box similar to that 

 used by Schafer and Moore in their in- 

 vestigations upon the spleen (see Fig. 

 99), can be moulded without difficulty 

 out of guttapercha. 2 The kidney hav- 

 ing been exposed by a lumbar incision, 

 is drawn out of the wound and placed 

 in the box. The pedicle of the kidney 

 passes out through a groove in one side 

 of the chamber. The box is closed by 

 a glass cover, and this is made air-tight 

 by a free application of thick vaseline. 

 The alterations in the volume of the 

 kidney are recorded by means of a 

 tambour. The tracing of renal volume 

 follows exactly the curve of arterial 

 pressure, and exhibits both the cardiac 

 and respiratory oscillations. 



By the use of Roy's oncometer, 

 Bradford 3 localised the renal vaso- 

 motor fibres to the anterior roots of 

 from the sixth to the thirteenth thoracic 

 nerves. Most of the renal vasomotor 

 fibres are found in the eleventh, 

 twelfth, and thirteenth nerves. 



By reflex excitation, it is more 

 common to obtain contraction than ex- 

 pansion of the kidney, but expansion is 

 frequently witnessed when the central 

 end of the eleventh, twelfth, and thirteenth posterior thoracic roots are 

 stimulated. Vaso-dilator fibres in the anterior roots are evidenced by 

 employing a slow rate of excitation (one per second). Rapid excitation of 

 the splanchnic nerve causes marked contraction of the kidney of its own 



Fig. 98. — Aortic pressure and renal 

 volume. Excitation of thirteenth 

 dorsal root. A, fast rate of excita- 

 tion contracts ; B, slow rate dilates 

 the kidney ; a, arterial pressure ; k, 

 kidney volume ; s, signal. — Bradford. 



1 Virchow'sArchvo, Berlin, 1883, Bd. xcii. S. 424. 



-Halliburton and Mott, "Proc. Physiol. Soc," Journ. Physiol., Cambridge and 

 London, 1897, vol. xxi. p. xviii. 



3 Journ. Physiol., Cambridge and London, 1889, vol. x. p. 358. See also Preobrasch- 

 ensky, Hermann's Jahresb., 1892, S. 74. 



