DESCRIBING AN ORGANISM. 203 



modification of the method of Griess. As reagents 

 the following solutions are employed: 



a. Naphthylamine ....... 0.1 gramme. 



Dist. water 20.0 c.c. 



Acetic acid (25 per cent, sol.) . . . . 150.0 c.c. 



6. Sulfanilic acid 0.5 gramme. 



Acetic acid (25 per cent, sol.) .... 150.0 c c. 



In preparing solution a the naphthylamine is dis- 

 solved in 20 c.c. of boiling water, filtered, allowed to 

 cool, and mixed with the dilute acetic acid. 



Solutions a and b are then mixed. The resulting 

 mixture should be colorless. It is best to prepare it 

 fresh as it is needed, though if kept in a closely stop- 

 pered flask it retains it virtues for some time. 



When added to cultures containing nitrites, in the 

 proportion of one volume to five volumes of the cul- 

 ture, a deep red color appears in a few seconds. If the 

 nitrites are not present, no color reaction occurs. In 

 making the test on cultures always control the results 

 by tests on the same medium not inoculated, as some of 

 the ingredients of which the medium is composed may 

 contain nitrites. Lunkewicz recommends the use of 

 Merck's peptone for this test, claiming that nitrites are 

 always to be found in Witte's peptones. 



POINTS TO BE OBSERVED IN DESCRIBING AN ORGANISM. 



The following is an outline of points to be considered 

 in describing a new organism or in identifying an 

 organism with one already described: 



1. Its source as air, water, or soil. If found in the 

 animal body, is it normally present or only in patholog- 

 ical conditions ? 



2. Its form, size, mode of development, occurrence of 



