180 Scientific Proceedings (68). 



nitrogen of the normal dog receiving a diet containing 0.4 gm. of 

 nitrogen per kilo is about 9 milligrams, the maximum being reached 

 about two hours after feeding with a return to the original level 

 in about 10 to 14 hours. By feeding excessive quantities of meat 

 the non-protein blood nitrogen may be increased 25 to 40 milli- 

 grams in 6 to 8 hours and the original level is usually not reached 

 even at the end of 24 hrs. In one animal (Dog 4) the blood 

 nitrogen did not reach its maximum until 14 hours after feeding; 

 the urinary nitrogen exhibiting a parallel gradual rise; this is 

 probably only to be explained on the basis of slow absorption 

 from the gastrointestinal tract. It is to be observed that this 

 animal received its allotment of water in small doses throughout 

 the day by stomach tube instead of in one large dose with its 

 feeding; this factor may have influenced the rate of absorption. 



The curve of the non-protein blood nitrogen in the normal 

 dog after feeding follows closely that of the urinary nitrogen. 

 There is frequently exhibited, however, a further or secondary 

 rise in the blood nitrogen at the time that the diuresis and output 

 of nitrogen in the urine is rapidly decreasing. 



In the fasting dog there occurs a gradual fall in blood nitrogen 

 to a minimum of from 12 to 18 milligrams, reached 30 to 48 hours 

 after the last feeding, and followed by a rise in the next few hours 

 to about 25 milligrams at about which level it tends to persist. 

 The urinary nitrogen shows a similar but less pronounced curve. 



The amount of urine influences the urinary nitrogen to a 

 much greater extent when the blood and urinary nitrogen values 

 are high than when they are low. Free diuresis induced by the 

 administration of water to the fasting animal has little effect 

 upon the nitrogen curves. 



The application of Ambard's formula to these data fails to 

 give a constant figure. Better results are obtained by the use of a 

 somewhat similar but simplified formula, but here also consider- 

 able discrepancies occur, and we have been unable to find any 

 formula that will constantly express the relation between blood 

 nitrogen, urinary nitrogen, and urinary amount. 



