CHAPTEE HI. 



METHODS OF BACTERIOLOGICAL STUDY- 

 STAINING, ETC. 



The study of micro-organisms by means of pure cultiures — Methods of 

 staining and mounting bacteria, their spores and flagella — The 

 imbedding and cutting of sections of tissues — The staining of micro- 

 organisms in sections. 



Fob the study of the growth of the bacteria, various 

 materials, both liquid and solid, have already been described 

 in the previous pages. The introduction of solid media by 

 Koch in 1881 inaugurated a new era in the progress of our 

 knowledge relating to the bacteria. It was o"bserved by 

 Koch that when a slice of cooked potato was exposed to the 

 air, and afterwards kept moist and at a suitable tempera- 

 ture in a covered chamber, small isolated dots and patches 

 made their appearance after a few days. The various 

 centres or colonies may present very different characters 

 both in shape and colour. It was found that each of 

 these points was made up of micrococci and bacilli, and in 

 nearly every case a pure cultivation or colony of a particu- 

 lar organism. Each individual organism which gained 

 access to the potato was fixed in situ, and, being unable 

 to move from the spot, commenced to grow, and in a short 

 time the rapid multiplication of the bacteria gave rise to a 

 colony, which soon became visible to the naked eye. 



It was these observations which led Koch to devise his 

 beautiful and simple methods of bacteriological study by 

 means of gelatine plate cultures. 



