THE HISTORY OF BACTERIOLOGY. 6 1 



lus xanthogenus, as giving rise during their growth in milk to 

 characteristic blue and orange colorations. He described the 

 exciting cause as small chain-like organisms, and considered 

 that they were the cause of both the colour formation and 

 the acid fermentive changes. As early as 1 819 we find the 

 first description of bleeding bread, the organismal cause of 

 which, Ehrenberg, in later years, was able to cultivate on 



Photo-micrograph of Bacillus Prodigiosus. x looo.— Organism forms beautiful 

 red colour of bleeding breadj bloody sweat, &c. 



various food media, boiled potatoes, Swiss cheese, and white 

 bread. He describes the organisms of which the coloured 

 mass was made up as being exceedingly minute, and as 

 having a characteristic movement quite distinct from the 

 so-called Brownian or molecular movement. 



Some idea of the size of these organisms may be obtained from Ehren- 

 berg's calculation that a cubic inch would contain from 46,656,000,000,000 

 to 884,736,000,000,000 plants ; this organism he called Monas prodigiosa. 



