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 1819 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 Procligiosus. x 1000. Organism forms beautiful 

 red colour of bleeding bread, 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 j this organism he called Monas prodigiosa, 



