ELIMINATION OF NITROGEN AND SULPHUR. 825 



to somewhat less than 1 gram per twenty -four hours (RIEDER, RUBNER). 

 Even with such food the absolute quantity of nitrogen eliminated by 

 the feces increases with the quantity of food because of the accelerated 

 digestion (TsuBoi J ), and is greater than in starvation. MtiLLER 2 found 

 in his observations on the faster CETTI that only 0.2 gram nitrogen was 

 derived from the intestinal canal. 



The quantity of nitrogen which leaves the body under norma^ circum- 

 stances by means of the hair and nails, with the scaling off of the skin, and 

 with the perspiration cannot be accurately determined. It is neverthe- 

 less so small that it may be ignored. Only in profuse sweating need the 

 elimination by this channel be taken into consideration. 



The view was formerly held that in man and carnivora an elimination 

 of gaseous nitrogen took place through the skin and lungs, and because of 

 this, on comparing the nitrogen of the food with that of the urine and 

 feces, a nitrogen deficit occurred in the visible elimination. 



This question has been the subject of much discussion and of numerous 

 investigations, the most recent by KROGH and OppENHEiHER. 3 These 

 researches have shown that the above assumption is unfounded, and 

 moreover several authorities, especially PETTENKOFER and VOIT, and 

 GRUBER, 4 have shown by experiments on man and animals that with 

 the proper quantity and quality of food the body can be brought into- 

 nitrogenous equilibrium, in which the quantity of nitrogen voided with: 

 the urine and feces is equal or nearly equal to the quantity contained in 

 the food; Undoubtedly we must admit, with VOIT, that a deficit of nitro- 

 gen does not exist, or it is so insignificant that in experiments upon metab- 

 olism it need not be considered. Ordinarily, in investigations on the 

 catabolism of proteins in the body, it is only necessary to consider the 

 nitrogen of the urine and feces, but it must be remarked that the nitrogen 

 of the urine is a measure of the extent of the catabolism of the proteins 

 in the body, while the nitrogen of the feces (after deducting about 1 gram 

 on a mixed diet) is a measure of the non-absorbed part of the nitrogen of 

 the food. The nitrogen of the food, as well as of the excreta, is generally 

 determined by KJELDAHL/S method. 



In the oxidation of the proteins in the organism their sulphur is oxidized 

 into sulphuric acid, and on this depends the fact that the elimination of 

 sulphuric acid by the urine, which in man is but to a small extent derived 



1 Rieder, Zeitschr. f. Biologie, 20; Rubner, ibid., 15; Tsuboi, ibid., 35. 



3 Berlin, klin. Wochenschr., 1887. 



2 See Regnault and Reiset, Annal. d. chem. et phys. (3), 26, and Annal. d. Chenu 

 u. Pharm., 73; Seegen and Nowak, Wien. Sitzungsber., 71, and Pfliiger's Arch., 25; 

 Pettenkofer and Voit, Zeitschr. f. Biologie, 16; Leo, Pfliiger's Arch., 26; Krogh, Skand. 

 Arch. f. Physiol., 18, and Wien. Sitz. Ber., 115, III: Oppenheimer, Bioch. Zeitschr., 4. 



4 Pettenkofer and Voit, in Hermann's Handbuch, 6, Thl. 1; Griiber, Zeitschr. f. 

 Biologie, 16 and 19. 



