22 Dairy Bacteriology. 



These culture methods are of essential importance in 

 bacteriology, as it is the only way in which it is possible 

 to secure a quantity of germs of the same kind. 



28. Use of the microscope in bacterial investiga- 

 tion. The microscope is in constant demand throughout 

 all the different stages of the isolating process in order 

 to verify the purity of the cultures. For this purpose, 

 it is essential that the instrument used shall be one of 

 strong magnifying powers (600-800 diameters) combined 

 with sharp definition, so that these tiny organisms shall 

 stand out clear and distinct. 



The microscopical examination of any germ is quite as 

 essential as the culture characteristics; in fact, the two 

 must always go hand in hand. This examination reveals 

 not only the form and size of the individual germ, but 

 the manner in which they are united with each other, 

 and any peculiarities of movement that they may possess. 



In carrying out the microscopical part of the work, not 

 only is the organism examined in a living condition, but 

 stained preparations are made by using solutions of anilin 

 dyes as staining agents. These are of great service in 

 bringing out almost imperceptible differences. The art 

 of staining has been carried to the highest degree of per- 

 fection in bacteriology, especially in the detection of 

 germs that are found in diseased tissues in the animal or 

 human body. 



In studying the peculiarities of any special organism, 

 not only is it necessary that these cultural and micro- 

 scopical characters should be closely observed, but special 

 experiments 'must be carried out along different lines, in 

 order to determine any special properties that the germ 

 may possess. Thus, the ability of any form to act as a 

 fermentative organism can be tested by fermentation ex- 

 periments; the property of causing disease, studied by 



