INFLUENCE OF NERVES UPON SECRETION OF KIDNEY. 515 



the renal arteries, particularly of the afferent vessels, must increase 

 the pressure in the glomeruli, and therefore the amount of filtered 

 fluid increases. The greater the measure in which the dilatation of 

 the vessels is confined to the distribution of the renal artery alone, 

 the greater will be the amount of urine. The lower dorsal nerves, in the 

 dog principally the twelfth and thirteenth, contain the largest number 

 of the vasomotor fibers for the kidney. 



Division of the renal plexus is, as a rule, followed by increase in the 

 amount of urine. Occasionally, in consequence of the increased pres- 

 sure, albumin is observed to pass into the Malpighian capsules; and with 

 rupture of the vessels of the glomeruli even blood may appear in the 

 urine. The center for these renal vasomotor fibers is situated on the 

 floor of the fourth ventricle, in front of the origin of the vagus. In- 

 jury, as by puncture, in this situation is, therefore, followed by increase 

 in the amount of urine (diabetes insipidus), occasionally with the simul- 

 taneous appearance of albumin and blood. Naturally, any injury of 

 the active nerve-path from the center to the kidney has a similar effect. 

 The center for the vasomotor nerves of the liver is situated close to 

 this center, and injury of the former gives rise to the production of 

 sugar in the liver. Eckhard observed hydruria develop after irritation 

 of the vermiform process of the cerebellum lying upon the medulla. 

 A similar result is brought about in human beings also as a result of irrita- 

 tion in this situation by tumors, inflammatory processes, and the like. 



If, in addition to the distribution of the renal artery, an adjacent 

 extensive vascular area be paralyzed simultaneously, the blood-pressure 

 in the distribution of the renal artery will be less high; as, at the same 

 time, much blood finds its way into the other paralyzed area. Under 

 such conditions, therefore, either a slight or only a transitory polyuria 

 will be observed. In this way, there results a moderate increase in 

 the amount of urine for a few hours after division of the splanchnic 

 nerve, which contains the vasomotor fibers for the kidney. These 

 leave the spinal cord in part through the first dorsal nerve, and pass 

 into the sympathetic nerve. The splanchnic contains, at the same 

 time, also the fibers for the extensive distribution of the intestinal 

 vessels. Irritation of this nerve is, naturally, attended with the op- 

 posite effect. 



If, with paralysis of the renal nerves, the overwhelming majority of 

 all of the vasomotors of the body are at once paralyzed, the pressure 

 throughout the entire arterial distribution falls in accordance with the 

 extensive dilatation of all of these vascular paths. In consequence, 

 the secretion of urine diminishes, even to the point of complete cessation. 

 This last effect is seen after division of the cervical cord down to the 

 seventh cervical vertebra. This fact explains the observation that the 

 polyuria that occurs after injury to the floor of the fourth ventricle dis- 

 appears as soon as the spinal cord down to the twelfth dorsal nerve 

 is divided. 



The presence of a large amount of urea in the blood causes con- 

 traction of the vessels of the body, but dilatation of the renal vessels. 



Contraction of the vessels, and, therefore, at the same time of the volume 

 of the kidney, are caused by asphyxia and strychnin-poisoning; also irritation of 

 sensory nerves has a similar reflex effect. Extirpation of the nerves of the kidney 

 has the opposite effect. During fever, the vessels of the kidney are contracted, 

 probably in consequence of irritation of the center by the abnormally heated blood. 



