APPENDIX 



NOTES ON TECHNIQUE 



Synopsis of Technique: General Methods of Examination; Staining Methods; 

 Flagella; Spores, etc. Bacteriological Diagnosis Examination of Water 

 Examination of Milk Bacteriological Diagnosis in Special Diseases 

 Examination of Malaria Blood Examination of Oysters Examination of 

 Sewage Miscellaneous. 



GENERAL ELEMENTARY METHODS OF EXAMINATION 



WITH the exception of pathological tissue and similar insoluble 

 substances, the common practice in bacteriology is to reduce as far as 

 possible the article to be examined to a fluid, that is to say, it is 

 chiefly fluids which can be systematically examined by the methods 

 of bacteriology. Water, milk, sewage, urine, blood, etc., are at once 

 in a condition to make examination available, but cheese, butter, foods, 

 soil, pus, dust, etc., require to be reduced to fluid, or washed in fluid 

 media, preparatory to examination. Thus soil particles may be washed 

 and macerated in sterilised broth, and the broth examined for contained 

 organisms. It will, on this account, be most convenient in the first 

 place to consider the application of bacteriological methods to the 

 examination of fluids. 



The principle underlying the ordinary technique is the solidification 

 of fluid gelatine at or below room temperature. If a drop of con- 

 taminated water, for example, be added _^ 



to a tube of 10 c.c. of liquid gelatine, ~~ 



thoroughly mixed, and then the contents 



of the tube poured out into a Petri plate 



(or other shallow glass dish) and allowed to FlG 38- _p e tri Dish 



solidify, we shall have scattered through 



the solid film of gelatine the contained bacteria, in a favourable medium 



for their growth and multiplication. Such a plate will be protected 



from the air and incubated at a regulated temperature. This is the 



principle of Koch's Plate Method. In the course of two or three days 



the film of gelatine on the plate becomes covered with colonies of 



germs, consisting of countless individual bacteria gathered round the 



453 



