160 TEXT-BOOK OF BACTERIOLOGY. 



potato culture will often be found useful. Let me here remark 

 that in future, whenever we speak of gelatin, etc., we always mean 

 a lOfo meat-peptone gelatin and \%% meat-peptone agar, unless some 

 other proportions are specially mentioned. 



The appearance of the colonies on the glass plate to the maxi- 

 mum of their development, as described, takes place in two or three 

 days of twenty-four hours, at an ordinary room-temperature of 14 

 to 20 C. 



Lastly, we shall consider any particular qualities that may 

 happen to distinguish the bacterium under treatment, and thus 

 collect all the particulars which contribute to give a full and exact 

 picture of each individual species. 



MICROCOCCUS PRODIGIOSUS. 



The prodigiosus is found in nature sometimes on substances con- 

 taining starch, on moist bread, boiled potatoes, and fresh-starched 

 linen, sometimes on hard-boiled white of egg, on meat, in milk, etc. 



Since its growth is accompanied by the development of a bright- 

 red coloring matter, we cannot be surprised that it excited atten- 

 tion in early times, and that it is one of the first bacteria that was 

 recognized as such. In times when people neither had nor could 

 have any idea of the existence of such things as micro-organisms, 

 the appearance of the prodigiosus led to the wildest suppositions. 

 All the cases of miraculous, blood-covered bread, weeping hosts, 

 etc., which are reported, may be safely referred to this bac- 

 terium, as may also those in which the reddening of bread was 

 supposed to result from diseased corn, and the reddening of milk 

 from a special disease of the cows. To determine the cause of the 

 latter special commissioners were appointed, but it was some time 

 before the real nature of the phenomenon was recognized. It was 

 Ehrenberg who first gave a good description of the " Monas pro- 

 digiosus," which has since retained this specific name. 



In consequence of its striking peculiarities, which make it rec- 

 ognizable at all times and without difficulty, the prodigiosus is a 

 favorite for experimental purposes. In all laboratories where bac- 

 terial labors are carried on it is, therefore, to be found, and with it 

 the beginner often makes his first modest attempt at bacterium 

 culture. 



The prodigiosus is not, properly speaking, a globular bacterium, 

 but a short rod, for one diameter of its cells considerably exceeds 

 the other. Chains of ten or more links are also occasionally ob- 

 served, particularly when the process of segmentation takes place 



