172 EXCRETION. 



days after the operation, the dog appeared to be uneasy, 

 cried frequently, and at 12 o'clock went into convulsions, 

 which continued until 3J- p. M., when he died. 



In one other instance, in which a dog was kept for more 

 than a year after extirpation, of one kidney, it was occasion- 

 ally 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 transmit- 

 ted 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 thus are 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 modifica- 

 tions 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 pres- 

 sure 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 



