68 GRAHAM LUSK 



rate and rapid. Bischoff could not find all the ingested nitrogen in the 

 urine and feces. (The urines, however, were frequently alkaline.) When 

 500 gm. of meat were given to dogs a third of the nitrogen content, or 

 6 gin. must have been eliminated in the respiration. As this contra- 

 dicted Regnault and Reiset, Bischoff concluded that the nitrogen was 

 probably expired in the form of ammonia. 



Perhaps Liebig's titration method might be wrong, so Voit devised a 

 method of distilling the ammonia derived from urine dropped upon soda- 

 lime. He made fifteen comparative tests, the first of which is thus 

 recorded : 



N content of 



5 c.c. urine 



in grams 



Liebig's method 0.2380170 



Soda lime method 0.2277660 



(The accuracy of this method of checking the results was subsequently 

 tested by Liebig himself and found to be correct.) 



Neither Bidder and Schmidt, nor Bischoff, nor Voit, ever observed 

 undigested meat in the feces of a dog. But the dry feces contained 6.41 

 and 6.52 per cent of nitrogen. 



Voit finds meat contains varying amounts of water and of nitrogen, 

 the latter between 3.41 and 3.69, with an average of 3.59 per cent. 

 Therefore, one cannot tell the exact composition of meat without some 

 degree of error. 



Forty kilograms of meat, if estimated at 3.4 per cent of nitrogen 

 and then at 3.5 per cent of nitrogen content, would mean a variation 

 of 40 gin. of nitrogen. 



Voit adopts the value 3.4 per cent, of nitrogen and he chooses well- 

 selected whole pieces of lean meat for his experiments in feeding animals. 



He always collects the urine freshly voided from a trained dog and 

 the urine is always acid. 



In this early work Voit gav$ to a dog weighing 27 kg. 1500 gm. of 

 meat for four days and collected the nitrogen eliminated in the urine, 

 feces and the bile. The dog lost 255 gm. in weight (this multiplied by 

 3.4 was believed to give the contribution of body protoplasm to the nitro- 

 gen excreted). The nitrogen balance read as follows: 



Grams Grams 



N in meat 1 204.00 N in urine 197.48 



N in lost body weight. . . 8.67 N" in feces 8.65 



N in bile 2.09 



212.67 



208.22 



