MECHANISM OF THE PRODUCTION OF URINE. 367 



intestine were found to be highly ammoniacal, and the secretions from these 

 parts, particularly the stomach, became continuous as well as increased in 

 quantity. Animals operated upon in this way usually live for four or five 

 days, and they then die in coma following convulsions. Toward the end of 

 life, the secretion of gastric and intestinal fluids becomes arrested, probably 

 from the irritating eifects of ammoniacal decomposition of their contents, 

 and then, and then only, urea is found to accumulate in the blood. 



The results obtained by other experimenters have generally corresponded 

 with those of Bernard and Barreswil. It has also been ascertained, as was 

 shown by Segalas and Vauquelin, that urea is an active diuretic when inject- 

 ed in small quantity into the veins of a healthy animal ; and that in this case, 

 it does not produce any poisonous effects, but is immediately eliminated. 

 When urea is injected into the vascular system of a nephrotomized animal, 

 it produces death in a very short time, with the characteristic symptoms of 

 uraemic poisoning. 



Experiments which were supposed to show that urea and the urates are 

 formed in the kidneys have been made with the view of comparing the effects 

 of removal of both kidneys with those produced by tying the ureters. Ac- 

 cording to these observations, the blood contains much more urea after the 

 ureters are tied than after removal of the kidneys. These experiments, 

 which are directly opposed in their results to the observations of Prevost and 

 Dumas, Bernard and Barreswil, Segalas, and many others, can not be accepted 

 unless it be certain that all the necessary physiological conditions were fulfilled. 

 In the first place, it was demonstrated, as early as 1847, that urea does not 

 accumulate in the blood immediately after removal of the kidneys, but that 

 this occurs only toward the end of life, and then urea is found in large quan- 

 tity. In the second place, it is well known that the operation of tying the 

 ureters is followed by a greatly increased pressure of urine in the kidneys, 

 which not only disturbs the eliminative action of these organs but affects 

 most seriously the general functions. Since the influence of the nervous sys- 

 tem upon the secretions has been closely studied, it is evident that the pain 

 and disturbance consequent upon the accumulation of urine above the ligat- 

 ed ureters must have an important reflex action upon the secretions ; and 

 this would probably interfere with the vicarious elimination of urea and of 

 other excrementitious substances by the stomach and intestines. It is well 

 known that an arrest of these secretions, in cases of organic disease of the 

 kidneys, is liable to be followed immediately by evidences of uraemia, and 

 that grave uraemic symptoms are frequently relieved by the administration of 

 remedies that act promptly and powerfully upon the intestinal canal. ' 



From a careful review of the important facts bearing upon the question 

 under consideration, there does not seem to be any valid ground for a change 

 in the ideas of physiologists concerning the mode of elimination of urea and 

 the other important excrementitious constituents of the urine. There is every 

 reason to suppose that these substances are produced in various tissues and 

 organs of the body during the process of disassimilation, are taken up by the 

 blood and are simply separated from the blood by the kidneys. 



