CHAPTEE V 



THE BIOLOGY OF MICROBES, ETC. 



IN this chapter we describe nearly all the more im- 

 portant microbes ; but the microbes present in such 

 diseases as tuberculosis, cholera, diphtheria, scarla- 

 tina, etc., will be described in Chapter vi. 



MICROCOCCI. 



Micrococcus prodigiosus. This microbe, which 

 measures from 0*5 to 1 //, in diameter, gives rise to a 

 blood-red pigment when grown on boiled potatoes, 

 white of egg, starch-paste, bread, agar-agar, and 

 other media. Fig. 30 represents the macroscopic 

 and microscopic appearances of -this microbe. It 

 grows well on agar-agar, which it liquefies. The 

 pigment, which M. prodigiosus gives rise to, is in- 

 soluble in water, but soluble in alcohol; and in 

 many of its reactions it resembles certain aniline 

 colours. 1 This pigment is only produced under cer- 

 tain conditions, viz., at a temperature of from 20 to 

 22 C., and after the gelatine or agar-agar has lique- 



1 Erdmann in Journal fur Praktische Chemie, 1866 ; and 

 Schroter in Beitrdge zur Biologie der Pfldnzen, vol. i. p. 109. 

 114 



