PART III. 



NON-PATHOGENIC BACTERIA. 



The number of varieties of non-pathogenic bacteria is very 

 large. Eisenberg* describes 376 species of bacteria, mostly 

 non-pathogenic. Sternberg f enumerates 489 species, including 

 the pathogenic varieties; but the majority, of course, are non- 

 pathogenic. Fliigge J considers about 500 species of bacteria. 

 Migula§ recognizes nearly 1300, and Chester || about 800 species. 

 Probably some of the bacteria which have been described as 

 distinct species are in reality not different; but, on the other 

 hand, it is also probable that a still larger number of species 

 have not been described at all — how many, it is impossible to 

 say. In a work of this character it is feasible to mention only 

 a few of the commonest and best-known species of non-patho- 

 genic bacteria. 



Micrococcus agilis. — Found in water; coccus about i [jl in 

 diameter, usually appearing as diplococci, sometimes as strepto- 

 cocci and tetrads; hquefies gelatin slowly; grows at room 

 temperature, on ordinary culture-media, forming a rose-red 

 pigment on agar and potato. This micrococcus is remarkable 

 in being actively motile; it possesses a flagellum. It is stained 

 by Gram's method. 



Micrococcus ureae. — ^Found in decomposed, ammoniacal 



* Bakleriologische Diagnostik. 1891. 

 t Manual of Bacteriology. 1893. 

 J Die Mikroorganismen. 1896. 

 § System der Bahterien. 1900. 

 II Manual of Determinative Bacteriology. 1901. 

 220 



