1906.] The Relation of the Kidneys to Metabolism. 81. 



two or three days of life. This terminal increase of nitrogen only occurs 

 when the cats have lost 22 per cent, or more of their body weight, and are 

 obviously in a state of inanition. The two cats which showed this terminal 

 increase of urinary nitrogen ate very little after the second operation, and 

 wasted rapidly. 



The effect of starvation upon the body weight and urinary nitrogen of 

 normal animals has been investigated by Voit, Schondorff, Kaufmann, and 

 others. It |is clear, from a comparison of their results with the condition 

 of our cats, that the condition of starving animals is identical with that of 

 cats which refuse food after the second operation on the kidneys. 



There is in both cases a progressive loss of weight, a fall of temperature 

 during the last few days of life, and usually a terminal rise in the output 

 of nitrogen in the urine. E. Yoit and others have shown that, in starvation, 

 the nitrogen output may increase several days before death, and that the time 

 of its onset is directly related to the amount of fat originally possessed 

 by the animal. A very fat animal may never exhibit the increase of 

 nitrogen, whereas, if the original store of fat is small, a very few days of 

 starvation suffice to evoke an increased output of nitrogen. For example, a 

 starving dog, observed by Schondorff, showed an increased output of nitrogen 

 when it had lost 20 per cent, of its weight ; in our cats the nitrogen rose 

 coincidently with a loss of 22 per cent, or more of the body weight. 



We consider, therefore, that the wasting, fall of temperature and final 

 increase of urinary nitrogen occur simply because the cats refuse food after 

 the second operation ; they die from inanition, and the rise of urinary 

 nitrogen, when it occurs, merely means that the animal's store of fat is much 

 diminished, and that more energy must be supplied by proteid breakdown. 



We consider, further, that the same explanation fully accounts for the 

 results obtained by Eose Bradford, and that there is no evidence from his 

 experiments that the kidneys directly influence nitrogenous metabolism. 



It may be added that Dr. Pembrey has investigated the gaseous exchange 

 of these cats ; he finds that his results are such as would be given by animals 

 in a state of inanition. 



III. The Amount and Concentration of the Urine. — The amount and specific 

 gravity of the urine of cats varies widely according to their diet. On a meat 

 diet the urine is concentrated ; on a milk diet it is abundant and dilute. 

 Making allowance for variations of diet, we find no evidence that the amount 

 and specific gravity of the urine are necessarily modified by either the first 

 or second operation. Only one cat almost invariably passed abundant 

 quantities of dilute urine after the first operation ; the others often passed 

 a concentrated urine. In this respect our results are at variance with those 



VOL. LXXIX. — B. G 



