224 



THE AMERICAN MONTHLY 



[December, 



of years. The matter in this article 

 has been mostly drawn from a contri- 

 bution to the Zeitsch. fiir Mikr.^ by 

 Dr. T. Stein. In a later number of 

 the same valuable publication Dr. 

 Henri Van Heurck has severely criti- 

 cised Dr. Stein for omitting due ref- 

 erence to Dr. Van Heurck's own ex- 

 periments and observations on the 

 subject. 



— o 



Chromegene Bacteria. 



Among the numerous species of 

 colored organisms classed among the 

 bacteria are some which are very 

 common, and as their culture may be 

 carried on with very simple appa- 

 ratus, such as can be readily arranged 

 by any one with the conveniences al- 

 ways at hand, their study offers a 

 good field for observers who have the 

 time and inclination to give it atten- 

 tion. There is also offered a promis- 

 ing field for original work, since 

 there is still much to be learned be- 

 fore the life cycles of these forms will 

 be fully known. 



In times past the sudden appear- 

 ance of colored spots upon cooked 

 articles of food has given rise to much 

 excitement among superstitious per- 

 sons. The so-called 'blood' which 

 has occasionally appeared myterious- 

 ly on bread, potatoes, etc., has doubt- 

 less been the Micrococcus prodigio- 

 sus^ which has a bright red color. 



The genus Micrococcus is the only 

 one belonging to Cohn's family of 

 bacteria. The Spherobacteria, char- 

 acterized by the spherical form of 

 their cells, which are always motion- 

 less. They are bacteria that produce 

 fermentation, and not putrefaction. 



The genus Micrococcus is divided 

 into three groups, viz., the chromo- 

 genes, zymogenes and the patho- 

 genes. The first are micrococci pro- 

 ducing colored pigments ; the second 

 are ferments of various kinds ; the 

 third are associated with diseases, as 

 M. septicus^ and the micrococcus dis- 

 covered by Salmon which is the cause 

 of swine-plague, of which we have an 



excellent and pure preparation. It is 

 only of the chromogenes that we have 

 now to speak. 



During the meeting of the Ameri- 

 can Association at Philadelphia we 

 visited the laboratory of Dr. Formad, 

 where he was cultivating, among other 

 things of the same nature, several of 

 the chromogenes, among them Mi- 

 crococcus prodigiosus^ M. luteus^ 

 and the species known to the Germans 

 as Rose-hefe, of which we have not 

 yet learned the scientific name. Dr. 

 Formad was good enough to place a 

 small quantity of each of these on a 

 slip of filter paper, which we pocket- 

 ed and brought home to Washington. 

 This was the seed from which we 

 have raised some fine cultures. 



It may be asked why we should 

 have desired such specimens to start 

 our cultures with when we are told in 

 the books that all one need do to ob- 

 tain them is to expose a proper nidus 

 for their development — a slice of po- 

 tato, for example — to the air, when 

 the spores will find their way to it 

 and grow. Well, the reason was 

 that, although occasionally a few stray 

 spores of the species desired may 

 be caught in this way, the probabili- 

 ties are that before the particular ones 

 sought are caught the potato will be 

 covered with something totally differ- 

 ent — most likely Bacillus subtilis^ 

 which is always about, and such a 

 rapid grower that it soon covers 

 everything it can live on. 



It is a very easy matter to obtain 

 cultures which will exhibit to the 

 naked eye the characteristic colors 

 and appearance of these organisms, 

 but to obtain them microscopically 

 uncontaminated with other species re- 

 quires more care. We will first de- 

 scribe the apparatus we have vised for 

 this purpose, and afterwards the pre- 

 cautions to be observed in making 

 absolutely pure cultivations. Any of 

 our readers who may desire to obtain 

 some of the spores to experiment 

 with can do so by sending a stamped 

 and addressed envelope to the editor. 

 We can supply M. luteus in any 



