Technic of Culture Manipulation 



203 



biers, racks, or otlier contrivances, and not lay tliem upon the table 

 so that the contents touch the stoppers. 



When the cotton plugs are removed in order that the contents of 

 the tubes or flasks may be inoculated or otherwise manipulated, the 

 removal and replacement should be done as quickly as convenient, 

 and the mouth of the tube should be flamed before removal. The 

 plugs should be held between the fingers, by that part which projects 

 above the glass, not laid upon the table, from which dust, and in- 

 cidentally bacteria, may be taken up and subsequently dropped into 

 the medium; nor must they be touched with the fingers at that part 

 which enters the neck of the container lest they take up micro- 

 organisms from the skin. The stoppers thus require careful con- 

 sideration lest they become the source of future contamination. 



So soon as the cotton stopper is 

 removed, the medium is left with- 

 out protection from whatever 

 micro-organisms happen to be in 

 the air, so that it should be re- 

 placed as soon as possible, and 

 every manipulation requiring its 

 removal performed expeditiously. 

 During the time the stopper is 

 withdrawn it is wise to hold the 

 tubes or other containers in an 

 oblique or horizontal position 

 that will aid in excluding the 

 micro-organisms of the air. Some 



Fig. 50.- 



Method of holding tubes 

 during inoculation. 



If the tubes are held obliquely, 



bacteriologists make inoculations 

 with the tubes reversed in all 

 cases in which solid media are 

 employed, but it is not necessary 



the danger of contamination is reduced to a minimum. It is well 

 to adopt some method of handling the tubes that has given satisfac- 

 tion to others and is found convenient to one's self and habitually 

 practise it until it becomes second nature and can be done without 

 thought. 



The usual method of making a transplantation of bacteria from 

 culture- tube to culture- tube, is, in detail, as follows: 



In order that any bacteria loosely scattered over the surface of the 

 cotton stopper, and upon the glass near the mouth of the tube, may 

 be destroyed and prevented from entering the medium as the stopper 

 is withdrawn, both the tube containing the culture and the fresh 

 tube to which it is to be transferred should be held for a moment in a 

 flame and rolled from side to side so that all parts are flamed. The 

 cotton ignites and blazes actively, but the flame can be extinguished 

 by forcibly blowing upon it and any smoldering remains extinguished 

 by pinching with the fingers. The tubes are now placed side by side 



