168 EXCRETION. 



after removal of the kidneys ; but that this occurs only after 

 tying the ureters, and the quantity seems to be greatest in 

 the first twenty-four or forty-eight hours after the operation. 1 

 Essentially the same results were obtained by Zalesky, 2 who 

 asserts that the proportion of urea in the blood after removal 

 of the kidneys in dogs is about the same as in the normal 

 condition. These experiments, which are directly opposed 

 in their results to the well-considered observations of Pre- 

 vost and Dumas, Bernard and Barreswill, Hammond, and 

 many others, cannot be accepted unless it be certain that all 

 the necessary physiological conditions have been fulfilled. 

 In the first place, it was positively demonstrated, as early as 

 184:7, that urea does not accumulate in the blood immediately 

 after removal of the kidneys, but only toward the end of 

 life, and then it is found in enormous quantity. 3 In the sec- 

 ond place, it is well known that the operation of tying the 

 ureters is followed by an immense pressure of urine in the 

 kidneys, which not only disturbs the eliminative action of 

 these organs, but affects most seriously the general functions. 



1 PERLS, in CANSTATT'S JahresbericM, Wurzburg, 1865, S. 194. The experi- 

 ments of Perls are not sufficiently extended to be very satisfactory. Rejecting 

 one experiment in which the animal was killed twenty-four hours after removal 

 of the kidneys when no accumulation of urea could be expected there are 

 three examinations of the muscular substance after death from removal of the 

 kidneys, and four after death from tying the ureters. In an examination after 

 removal of the kidneys, 2'32 parts per 1,000 of nitrate of urea were found ; in 

 the second, there were no crystals in the extract ; and in the third there were 

 slight traces of urea. These animals died three or four days after the opera- 

 tion. Five examinations were made of the muscular substance in animals 

 that died after tying the ureters. In three of these examinations, urea was 

 found in considerable quantity ; and in the remaining two, urea was present in 

 very small quantity in one instance, and in the other, it is not stated that any 

 urea was found. No examinations were made of the blood. These experi- 

 ments on the accumulation of urea in nephrotomized animals are hardly suffi- 

 cient to overthrow the researches of Prevost and Dumas, and others by whom 

 their observations have been confirmed. 



2 ZALESKY, Untersuchungen uber den urcemischen Process und die Function der 

 Nieren, Tubingen, 1865. 



8 BERNARD AND BARRESWILL, loc. cit. 



