632 APPLICATION OF METHODS OF BACTERIOLOGY 



and in thickness from 0.2 to 0.3 /z. The whole organism 

 is very flexible and has highly motile end-portions. No 

 undulating membrane'. 



Divide's transversely. 



Stains reddish violet by the Giemsa method (see Fig. 

 108). When obtained in culture it is soluble in 10 per 

 cent, bile salts; insoluble in 10 per cent, saponin. 



Detection by Microscopic Examination. The methods 

 commonly employed in searching for these organisms are: 

 The microscopic examination of fresh unstained prepara- 

 tions by means of the dark-field illumination (see the 

 method), or by the examination of stained smears. In 

 the former method the organisms are recognized as color- 

 less, brightly illuminated, motile threads or spirals that 

 stand out in striking contrast to the almost black field 

 through which they are moving. If the necessary equip- 

 ment is available this is by far the quickest and most direct 

 method of getting positive indications. 



By the latter method the organisms are seen as. fixed, 

 stained undulating threads or spirals according to their 

 nature. In this method the examination is of smears made 

 as follows: The smears are made in the routine way on 

 either clean cover slips or slides. They are then allowed 

 to dry in the air, after which they are fixed in pure methyl 

 alcohol for three or four minutes. They may then be stained 

 by the Giemsa method or by some one or another of the 

 silver impregnation, methods. 



STAINING SOLUTION. 



Azure II (eosin) 0.30 grams 



Azure II . ... 0.08 u 



