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APPENDIX 



parent organism which found its way thither from the drop of con- 

 taminated water. The next step is to examine these quantitatively 

 and qualitatively. 



1. Naked-Eye Observation of the Colonies. — By this means, at the very 

 outset certain facts may be obtained, viz., the size, elevation, configura- 

 tion, margin, colour, grouping, number, and kinds of colonies, all of 

 which facts are of importance, and assist in final determination as to the 

 quantity and character of the organisms present in the original drop of 



Fifi. 89.— A Diagram of Colonies of Bacteria on a Gelatine Plate. 



water. Moreover, in the case of gelatine medium (owing to the fact 

 that it is liquefiable by ferments), one is able to observe whether or not 

 there is present what is termed liquefaction of the gelatine. Some 

 organisms produce in their development a peptonising ferment which 

 breaks down gelatine into a fluid condition. Many have not this power, 

 and hence the characteristic is used as a diagnostic feature. 



2. The Microscopic Examination of Colonies (under low magnification, 

 X 60-100) confirms or corrects that which has been observed by the naked 

 eye. Micro-organisms, when growing in colonies, produce cultivation 

 features which are peculiar to themselves (especially is this so when 



