VARIATIONS IN THE SECRETION OF URINE. 405 



at 12 o'clock went into convulsions, which continued until 3 p. M., when he died. 

 In one other instance, in which a dog was kept for more than a year after extirpa- 

 tion of one kidney, it was occasionally observed that the animal was rather quiet and 

 indisposed to move for a day or two, but this always passed off, and when he was 

 killed he was as well as before the operation. 



Influence of the Nervous System, Blood-pressure, etc., upon the Secretion of Urine. 

 There are numerous instances in which very marked and sudden modifications in the 

 action of the kidneys take place under the influence of fear, anxiety, hysteria, etc., 

 when the impression must have been transmitted through the nervous system. Although 

 little is known of the final distribution of the nerves in the kidney, it has been ascertained 

 that here, as elsewhere, filaments from the sympathetic system ramify upon the walls of 

 the blood-vessels, and they are undoubtedly capable of modifying the quantity and the 

 pressure of blood in these organs. 



It may be stated as a general proposition, that an increase in the pressure of blood in 

 the kidneys increases the flow of urine, and that, when the blood-pressure is lowered, 

 the flow of urine is correspondingly diminished. This fact will in a measure account for 

 the increase in the flow of urine during digestion ; but it cannot serve to explain all of 

 the modifications that may take place in the action of the kidneys. The fact above 

 stated, although it has been long recognized by physiologists, has lately been very fully 

 illustrated by the experiments of Bernard. This observer measured the pressure of blood 

 in the carotid artery of a dog and carefully noted the quantity of urine discharged in the 

 course of a minute from one of the ureters. Afterward, by tying the two crural, the two 

 brachial, and the two carotid arteries, he increased the blood-pressure about one-half, and 

 the quantity of urine discharged in a minute was immediately increased by a little more 

 than fifty per cent. In another animal, he diminished the pressure by taking blood from 

 the jugular vein, and the quantity of urine was immediately reduced about one-half. 

 His later observations on this subject showed that the increase in the quantity of urine 

 produced by exaggerated pressure of blood in the kidneys was capable of being modified 

 through the nervous system. In these experiments, the nerves going to one kidney were 

 divided, which produced an increase in the arterial pressure and a consequent exaggera- 

 tion in the quantity of urine from the ureter on that side. The pressure was then farther 

 increased by stopping the nostrils of the animal. The quantity of urine was increased by 

 this on the side on which the nerves had been divided, but the pain and distress from 

 want of air arrested the secretion upon the sound side. 



The precise influence which special nerves exert upon the secretion of urine has not 

 yet been positively ascertained. 8ome important facts, however, bearing upon this sub- 

 ject have been developed of late years. In his interesting and novel experiments upon 

 artificial diabetes in animals, Bernard found that, when irritation was applied to the floor 

 of the fourth ventricle, in the median line, exactly in the middle of the space comprised 

 between the origin of the pneumogastrics and the auditory nerves, the urine was in- 

 creased in quantity and became strongly saccharine. When the irritation was applied a 

 little above this point, the urine was simply increased in quantity, but it contained no 

 sugar ; and, when the puncture was made a little below, sugar appeared in the urine, 

 without any increase in the quantity of the secretion. It has also been observed that 

 section of the spinal cord in the upper part of the dorsal region arrests, for a time, the 

 secretion of urine. 



The final effect of division of all the nerves going to the kidney is very curious. The 

 immediate effect of destruction of these nerves is to increase largely the amount of blood 

 sent to the kidney, the organ then pulsating like an aneurismal tumor. In experiments 

 upon this subject, by Milller and Peipers, the flow of urine was sometimes arrested by divi- 

 sion of these nerves, but occasionally it continued. In these observations, the nerves 

 were destroyed by applying a ligature tightly to the vessels as they enter at the hilum, 



