METHODS OF PURE CULTURE STUDY 119 



conditions are known under which the organism in question 

 produces vigorous growth, it should be studied without prelimi- 

 nary cultivation as soon as possible after isolation from its 

 natural habitat. Such an organism is not likely to give good 

 growth on any ordinary media, and the results of the study 

 called for by the chart will have little significance. 



STUDY OF MORPHOLOGY 



The routine study of morphology should be from dried prep- 

 arations, stained with fuchsin, methylen blue, or gentian violet. 

 Preparations to show the vegetative cells should be made, 

 preferably, from agar slant cultures, from a few hours to two 

 days old, according to the rapidity of growth. The medium 

 and temperature used and the age of the culture should be 

 recorded. 



Motility. Hanging-drop preparations of young broth or 

 agar cultures should be examined for motility. If motile, micro- 

 scopic preparations should be made to show the arrangement of 

 the flagella, using any of the ordinary methods of flagella stain- 

 ing with which the student can obtain good success. Even if 

 motility is not observed in hanging-drop, it is wise to attempt a 

 flagella stain, because motile organisms often lose their motility 

 under the conditions of observation. Even negative results from 

 both hanging-drop preparation and flagella stain do not abso- 

 lutely prove that the organism is immotile. 



Presence of spores. Routine examinations for spores should 

 be made on stained, dried preparations from agar slant cultures 

 a week old. Stain with methylen blue. Vegetative forms take 

 the stain, but spores do not. In most cases there will be no 

 trouble in finding spores if the organism produces them. All 

 rather larger rods however, (0.8 micron or more in diameter) 

 should be regarded. as possible spore-producers, even though 

 microscopic examination does not show spores. Such bacteria 

 should be mixed with sterile water and heated to 85°C. for ten 

 minutes; if still alive, spores may be regarded as unquestionably 

 present. Also make repeated transfers of the culture onto agar 



THE JODENAL OF B ACTERIOLOQT, VOL. Ill, NO. 2 



