166 EXCRETION. 



almost unquestioned ; viz., that urea is simply separated 

 from the blood by the kidneys ; but the more recent obser- 

 vations of Bernard and Barreswill, Hammond, and others, 

 while they confirm the first experiments on this subject, 

 have added very considerably to our knowledge of the 

 mechanism of ursemic poisoning after extirpation of the 

 kidneys. The kidneys, it has been found, can readily be 

 removed from living animals, dogs, cats, rabbits, etc., with- 

 out any great disturbance immediately following the opera- 

 tion. Bernard and Barreswill found that animals from 

 which both kidneys had been removed did not usually pre- 

 sent any distinctive symptoms for a day or two after, except 

 that they vomited and passed an unusual quantity of liquid 

 from the intestinal canal. During this period, the blood 

 never contained an abnormal quantity of urea ; but the 

 contents of the stomach and intestine were found to be 

 highly animoniacal. During this time, also, the secretions 

 from the stomach and intestines, particularly the stomach, 

 became continuous, as well as increased in quantity. Ani- 

 mals operated upon in this way usually live for four or five 

 days, and then die in coma following upon convulsions. 

 Toward the end of life, the secretion of gastric and intestinal 

 fluids becomes arrested, probably from the irritating effects 

 of ammoniacal decomposition of their contents, and then, and 

 then only, urea is found to accumulate enormously in the 

 blood. 1 



It is thought by Bernard that the hypersecretion by the 

 gastric and intestinal mucous membrane, in nephrotomized 

 animals, is an effort on the part of the system to eliminate 

 the urea, which is decomposed by contact with these mem- 

 branes into carbonate of ammonia. This view is sustained 

 by the fact that when urea is introduced into the alimentary 

 canal in living animals, it disappears almost immediately 



1 BERNARD, Liquides de Vorganisme, Paris, 1859, tome ii., p. 36, el seq. These 

 experiments were first published by Bernard and Barreswill in the Archives ge- 

 nerates de medecine, Paris, 1847, tome xiii., p. 449. 



