528 BIOLOGY OF THE MICRO-ORGANISMS. 



sible albuminoid materials.* Ammoniacal salts are not 

 so suitable, but are better borne than in the case of the 

 yeast fungi. The remaining nitrogenous compounds 

 appear to have the same relative value as in the case of 

 the mould fungi ; according to Niigeli, the nitrogen can 

 also be obtained from nitrates, and in the experiments in 

 question it was possible to follow the gradual reduction 

 of the nitric acid to nitrous acid, and finally to ammonia. 



Beduction of This reduction of nitrates by bacteria has been recently 

 observed by Gayon and Dupetit, Deherain, Maquenne, 

 and Springer. Anaerobic organisms similar to or iden- 

 tical with bacillus butyricus when they set up a fermen- 

 tation, combined with the development of hydrogen, 

 seem to cause reduction of nitrates with formation of 

 oxide of nitrogen. This was also the case with certain 

 aerobes, and to a less extent with the bacilli of chicken 

 cholera, anthrax, &c.*f- In all these experiments, how- 

 ever, it is probable that the nitrates did not suffice to 

 provide the necessary oxygen for the fission fungi, but 

 that reduction was a secondary phenomenon, caused by 

 other products of the tissue change or fermentation, and 

 only accompanying the true tissue change of the bacteria. 



carbon* f ^^ e SU PP^ ^ carDon ^ s obtained not only from sugar 



but also from bodies similar to it, from glycerine, and 

 especially from the various salts of fatty acids, such as 

 the alkaline salts of tartaric acid, citric acid, malic acid, 

 mucic acid, lactic acid, acetic acid, &c. ; even those 

 compounds which act, when markedly concentrated, in 

 a decidedly poisonous manner on the bacteria can be 

 utilised in a very dilute state as sources of carbon 

 supply, for example, carbolic acid, salicylic acid ; further, 

 aethylic alcohol, which forms the most favourable nutrient 

 medium for the vinegar fungus, and which can be present 

 in the nutrient solution up to 10 per cent. It is remark- 

 able that, according to Pasteur's observations, it is only 



* See more especially Nageli, I.e. Cohn, Beitriige, vol. i., Heft 2. 

 Bucholtz, Arch.f. Exper. Path., B. 7, S. 81. Mayer u. Knierim, Landw. 

 Versuchsstat., vol. 16 (Essigpilz). v. Jacksch (Harnstoffpilz), Zeitschr. 

 f. physiol. Ckemie, vol. 5. 



t Gayon and Dupetit, Compt. Rend., vol. 95. Deherain and Ma- 

 quenne, ibid., and vol. W.Bult soc. c/iim, 2, 3D. Springer, Chew., Ber., 

 vol. 16. 



