BACTERIOLOGICAL TECHNIQUE 33 



second flask of water. Again mix by shaking, and if the liquid 

 then appears sKghtly opalescent the right dilution has probably 

 been obtained ; transfer a drop of the mixture to a Freuden- 

 reich fla,sk containing wort gelatine and mix thoroughly. Then 

 spread a drop of the wort gelatine mixture in a thin layer on 

 the cover glass by means of a glass rod, and place the glass on 

 the glass plate underneath the bell jar and leave imtil the 

 gelatine is set. Prepare a Botcher chamber by placing a 

 smaU drop of water at the bottom of the weU and smearing 

 the edge of the ring with vaseline, next reverse the glass with 

 the gelatine film and adjust it to the ring of the chamber ; 

 the preparation should then be transferred to the microscope 

 for examination. The lowest-power objective with which the 

 yeast cells can be distinctly seen should be employed. For 

 the purpose of obtaining colonies those cells are chosen which 

 are several millimetres apart from other cells, and their position 

 must be carefully recorded, a diagram being made to indicate 

 the position of the ceUs chosen. 



After marking the position of several cells keep the culture 

 at a temperature of about 20°, and examine it from day to day 

 with the microscope, as the ceUs multiply, in order to be sure 

 that no cells in the immediate vicinity of the colonies have 

 been overlooked. When the colonies are large enough a pure 

 culture in wort may be obtained from each colony by inocu- 

 lation in the manner described for gelatine plate culture. 



Permanent preparations sufficient to show the general form 

 of the yeast cells can be stained and mounted in a similar 

 manner to bacteria ; special methods are necessary to render 

 clearly visible the inner structure of the cell and to stain 

 spores. 



Examination of Mould Culture. — Suitable culture media 

 can be inoculated with moulds in a manner similar to the 

 methods used for bacteria. As moulds are aerobic organisms, 

 the method of inoculation on gelatine may be used, in which 



