428 PHYSIOLOGY CHAP. 



heart are retarded or suspended, causes a fall of aortic pressure 

 accompanied by a diminished flow of urine, which becomes normal 

 ; i gain when the ordinary cardiac rhythm is re-established. From 

 the two ureters of a dog, (loll collected 915 grins, urine every 30 

 minutes under normal conditions ; 10 grins, after division of the 

 vagi; 2'36 grins, during the stimulation of one vagus; 7'22 grins, 

 immediately after cessation of the stimulus. 



When aortic -pressure is raised by tying the large arteries, the 

 amount of urine eliminated increases proportionally. Thus in an 

 experiment in which Goll tied both carotids, both femorals, and 

 both cervical arteries, the aortic pressure rose from 127 to 142 mm. 

 Hg, and the amount of urine secreted increased from 8'7 grins, 

 to 21 grins, every 30 minutes. 



Transverse section of the cervical cord suspends the flow of 

 urine, by lowering aortic pressure. This fact was first determined 

 by Cl. Bernard (1859), and was more closely studied by Ustimo- 

 witsch with Ludwig (1870), and by Griitzner with Heidenhain 

 (1875). According to the former the secretion is arrested when 

 the aortic pressure sinks to 40-50 nun., according to Griitzner when 

 it falls to a value of 30 mm. 



When aortic pressure is constant, the urinary secretion can be 

 modified by increasing or diminishing the resistance which the 

 blood encounters in passing through the Malpighian glomeruli. 

 Thus Max Herrmann (1859), in Ludwig's laboratory, showed that 

 it was possible by moderate compression of the renal artery to 

 retard the secretion of urine, while by occluding the vessels it can 

 be entirely suppressed. In exceptional cases, however, in certain 

 animals, the secretion of urine continues, though much reduced, 

 even after ligation of the renal arteries. This is explained by the 

 fact that in these animals capsular arteries exist which are 

 capable of supplementing the large artery that enters by the 

 hilum. 



Division of the nerve filaments which accompany the renal 

 artery to the point at which it enters by the hilum produces 

 vasornotor paralysis of the kidney, so that it increases in volume 

 and secretes a larger amount of urine (Bernard, 1859 ; Eckhard, 

 1869). The polyuria commences after a brief secretory pause, 

 augments progressively, and reaches its maximum after 30-60 

 minutes. The urine secreted after section of the nerves of the 

 renal plexus not infrequently contains albumin, and also haemo- 

 globin (Krimer and others) ; but this fact is not constant and 

 depends on the gross alterations in the circulatory conditions of 

 the kidney due to the effects of operation. In fact, when the 

 principal nerve filaments are divided with great care, polyuria is 

 produced without albuniinuria or haemoglobinuria (Herrmann). 



If, instead of section, the renal nerves are electrically stimulated, 

 a vaso-constriction results which diminishes or arrests the secretion. 



