212 



Cultures, and their Study 



stopper is withdrawn it is wise to hold the tubes or other 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. Thus, a tube 

 held vertically can probably more easily receive such organ- 

 isms than one held horizontally or reversed. Some bacteri- 

 ologists make inoculations with the tubes reversed in all cases 

 in which solid media are employed, but it is not at all neces- 

 sary. If the tubes are held obliquely, the danger of con- 

 tamination is reduced to a minimum. It is well to adopt 

 some method of handling the tubes that has given satis- 

 faction 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 cul- 

 ture-tube is, in detail, as 

 follows : 



In order that any bac- 

 teria loosely scattered 

 over the surface of the 

 cotton stopper, and upon 

 the glass near the mouth 

 of the tube, may be de- 

 stroyed and prevented 

 from entering the med- 

 ium as the stopper is with- 

 drawn, both the tube con- 

 taining 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 smolder- 

 ing remains extinguished by pinching with the fingers. The 

 tubes are now placed side by side between the thumb and 

 upward-directed palm of the left hand, the stoppers toward 

 the operator. The position of the tubes should be such as 

 to permit one to see the contained media without the fingers 

 being in the way. The stopper of the tube toward the 

 left is removed by a gentle twist and placed between the 

 index and middle fingers of the left hand; the stopper of 

 the next tube similarly removed and placed between the 



Fig. 40. Method of holding tubes 

 during inoculation. 



