368 EXCKETION BY THE SKIN AND KIDNEYS. 



Extirpation of one kidney from a living animal is not necessarily fatal. 

 If the operation be carefully performed, the wound will generally heal with- 

 out difficulty, and in most instances the remaining kidney seems sufficient 

 for the elimination of urine for an indefinite period. In a large number of ex- 

 periments, the animals killed long after the wound had healed never pre- 

 sented any marked symptoms of retention of excrementitious matters in the 

 blood, except in one or two instances. It is a noticeable fact, however, that 

 in many instances they showed a marked change in disposition, and the ap- 

 petite became voracious and unnatural. These animals would sometimes eat 

 faeces, the flesh of dogs, etc., and, in short, presented certain of the phenom- 

 ena so frequently observed after extirpation of the spleen (Flint). After 

 extirpation of one kidney, it has been observed that the remaining kidney 

 increases in weight, although investigations have shown that this is due 

 mainly to an increase in the quantity of blood, lymph and urinary matters, 

 and not to a new development of renal tissue. The following is an excep- 

 tional experiment in which the animal died after extirpation of one kidney : 

 One kidney was removed from a small cur-dog, about nine months old, by 

 an incision in the lumbar region. The animal did not appear to suffer from 

 the operation, and the wound healed kindly. The only marked effects were 

 great irritability of disposition and an exaggerated and perverted appetite. 

 He would attack the other dogs in the laboratory without provocation, and 

 would eat with avidity, faeces, putrid dog's flesh and articles which the other 

 animals would not touch and which he did not eat before the operation. 

 Forty-three days after the operation, the dog appeared to be uneasy, cried 

 frequently, and went into convulsions, which continued for about three 

 hours, when he died (Flint, 1864). In one other instance, in which a dog 

 was kept for more than a year after extirpation of one kidney, it was occa- 

 sionally 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 Blood-pressure, the Nervous System etc., upon the Secre- 

 tion of Urine. There are many instances in which very marked and sudden 

 modifications in the action of the kidneys take place under the influence of 

 fear, anxiety, hysteria etc., which must operate 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, vaso-motor nerves are distrib- 

 uted to the walls of the blood-vessels, and they are capable of modifying the 

 quantity and the pressure of blood in these organs. 



It may be stated as a general proposition, ths-t 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 

 will in a measure account for the increase in the flow of urine during diges- 

 tion ; but it can not serve to explain all of the modifications that may take 

 place in the action of the kidneys. Bernard measured the pressure of blood 

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

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



