126 ATLAS OF BACTERIOLOGY. 



fermentation are products of metabolism like all the 

 other products of the bacterial cell, and hence a di- 

 vision of fermentations in principle is not warranted. 

 But it will be advisable to discuss the individual bac- 

 terial products according to their development upon 

 a saccharine or non-saccharine nutrient medium, and 

 then to add some functions of the bacteria which are 

 manifested by decomposition of salts of the fatty 

 acids, alcohols, etc. 



A. Functions upon which, the Amount of 

 Sugar in the Nutrient Medium Exerts 

 no Great Influence. 



1. Formation of Pigment. 



The chemistry of the pigment matters has been 

 very little studied, but in recent times a preliminary 

 survey has been made by some of Migula's pupils. 

 In regard to the fluorescent pigments I follow the 

 statements of K. Thumm ( " Arbeiten d. bact. Instituts 

 Karlsruhe," published by Klein and Migula, Vol. I., 

 Pt. 3, p. 291) and those of Paul Schneider (eod. loco, 

 Vol. I., Pt. 2, p. 201) in regard to the other pigments. 



1. Ked and Yellow Pigments. According to 

 Schneider the twenty -seven yellow and red bacte- 

 ria furnish, in almost all cases,* pigments which are 

 soluble in alcohol, insoluble in water, f and are also 



* The coloring matter of micrococcus cereus flavus Passet was 

 soluble only in dilute caustic potash. 



f A striking contrast to these results is furnished by M. Freund 

 (C. f. B., xvi., 640). In examining four newly discovered red 

 and yellow bacteria he found the pigment always soluble in 

 water, and insoluble in alcohol and ether. 



