A STUDY OF CERTAIN SAPROPHYTIC BACTERIA 67 
one from the other. To identify species, therefore, one must 
compare the cultural characters of the organism in question 
with the description of the species already known. As new 
media are constantly being introduced, one often finds that the 
descriptions given in text-books and manuals of bacteriology 
are very brief and, as compared with modern requirements, 
insufficient to identify the species. This has resulted in the 
listing of a very large number of species that are very difficult, 
if not impossible, to identify. With pathogenic bacteria the 
somewhat specific action on experimental animals affords much 
aid in their identification. For further explanations, see text- 
books. Matzuschita’s Bacteriologische Diagnostk is especially 
helpful in diagnosing species. ‘ 
The descriptive chart of the Society of American Bacteri- 
ologists for the identification of species is very convenient for 
recording the morphological, cultural, physical, chemical, and 
pathogenic properties of bacteria. 
13 Dilution. 
9-Z 
