128 MANUAL OF BACTERIOLOGY. 



CHAPTER II. 



PRODUCTS OF THE GROWTH OF BACTERIA. 



Phosphorescence. Bacteria whose cultures exhibit phos- 

 phorescence have been found in the ocean and in fish. 



Chromogenic Bacteria. Many bacterial growths display 

 brilliant coloring. The different species of sarcinse are 

 remarkable for forming highly-colored growths; some of 

 them are rose-red, some orange-yellow, some lemon-yellow, 

 and so on. The bacillus prodigiosus presents a brilliant red 

 growth whose rapid development is said to have formed the 

 basis for the so-called " Miracle of the Bleeding Host " (see 

 page 15). The bacillus pyocyaneus in culture gives a bril- 

 liant green fluorescence and is responsible for the color of 

 blue or green pus. 



Bacilli which exhibit a green fluorescence in cultures are 

 common in water. In cultures on potato or agar the colors 

 of the chromogenic forms are usually well shown. 



Ferments or Enzymes. 1 Many bacteria form ferments 

 which have the power of dissolving proteid substances in 

 a manner similar to trypsin. The liquefaction of gelatin 

 is a familiar example of this process. The property of 

 liquefying gelatin, or otherwise, is used in classifying bac- 

 teria and in determining the nature of unknown species. 



Some bacteria, as the bacillus coli communis, form fer- 

 ments which act like rennet in coagulating milk. Other 

 bacteria are capable of forming sugar from starch. Others 

 have the power of changing cane-sugar into glucose. 



1 Consult Buxton, " Mycotic Enzymes," American Medicine, July 25, 

 1903- 



