Adexey — Aerobic Bacteria/ Fermentation. 15 



Of the oxygen consumed, 83-91 per cent, was taken up by the 

 respiratory changes, and 16*09 per cent, by other physiological pro- 

 cesses not examined. 



On comparing together the analytical results recorded for the next 

 three experiments, Xos. 7, 8, and 9, Table III., it is evident that No. 7 

 marks the point when the change of all the urea originally present had 

 just been completed ; while Nos. 8 and 9 mark well-advanced steps 

 in true nitrification of the ammonia. 



In the case of No. 7, 67*8 per cent, and 64*6 per cent., respec- 

 tively, of the total carbon dioxide and inorganic nitrogen products 

 were the result of respiratory change ; and 32'2 per cent, and 30-7 per 

 cent., respectively, of the same products were the result of enzymic 

 action, leaving, in the case of the latter products, 4*7 nitrogen as 

 ammonia unaccounted for. 



Of the oxygen consumed, 86*5 per cent, was taken up by the 

 respiratory changes, and 13*5 per cent, by other physiological pro- 

 cesses not examined. 



Although experiment 7 illustrates the complete fermentation of 

 the urea originally present, the total volume of carbon dioxide formed 

 only accounts for 77*96 per cent, of the carbon which the urea 

 originally contained ; and the total inorganic nitrogen products account 

 for only 81*9 per cent, of the nitrogen originally present in the same. 

 It may therefore be assumed that the balance of carbon, nitrogen, and 

 atmospheric oxygen — viz., 22*04 per cent., 18*1 per cent., and 13*5 per 

 cent., respectively — were taken up by other physiological processes. 



Experiments ivitli Urea and Rochelle Salt. 



The following experiments confirm, in an interesting way, the fact 

 borne out by experiments 1, 2, and 3, Table I., viz., that the enzymic 

 action was not exerted by the organisms upon urea during the earliest 

 stages of their development. 



These experiments were made with a solution, in distilled water, of 

 urea and inorganic salts of similar strength as the preceding solutions, 

 but containing in addition 0'141 grm. per litre of Eochelle salt, 

 a quantity equivalent to 44*64 c.c. of carbon dioxide. This latter 

 substance was selected as being a very suitable organic nutrient for 

 the organisms capable of hydi'olizing urea (see Jaksch, Zeitschr. f . phys. 

 Chem. 1881). 



