64 



METHODS OF CULTIVATION OF BACTERIA. 



nected from the hydrogen apparatus. In the case of flask (2), 

 first the exit tube and then the entrance tube are sealed off in the 

 flame before the flask is disconnected from the hydrogen ap- 

 paratus. It is well in the case of both flasks to run some melted 

 paraffin all over the rubber stopper. Sometimes much gas is 

 evolved by anaerobes, and in dealing with an organism where 

 this will occur, provision must be made for its escape. This is 

 conveniently done by leading down the exit tube, and letting 

 the end just dip into a trough of mercury (Fig. 28), or into mer- 

 „ cury in a httle bottle tied on to the 



end of the exit tube. The press- 

 ure of gas within causes an escape 

 at the mercury contact, which at 

 the same time acts as an efficient 

 valve. The method of culture in 

 fluid media is used to obtain the 

 soluble products of such anaerobes 

 as the tetanus bacillus. 



Dr. W. H. Park of New York 

 has recently introduced a very 

 simple method for making anae- 

 robic cultures in fluid media. 

 An Erlenmeyer flask containing 

 a suitable quantity of medium is boiled in a water bath for 

 ten or fifteen minutes, to drive off all dissolved oxygen, then 

 rapidly cooled down and inoculated. Hot melted parafifin is 

 now poured into the flask until it reaches a depth of 2 or 3 mm., 

 and upon solidifying it forms a perfect seal, excluding the air 

 completely, yet not adhering to the glass so strongly as to 

 prevent escape of gases should any be formed by the growing 

 anaerobes. 



Wright's Method of Anaerobic Culture. — Utilising Buchner's 

 pyrogallic acid medium for the removal of oxygen, Wright has 

 contrived two very ingenious methods for anaerobic culture in 

 ordinary test-tubes. In the first method, which is applicable to 

 both solid and fluid media (Fig. 29), after inoculating,- the cotton 

 plug, always made of absorbent cotton, is cut oflF flush with the 

 extremity of the tube, and pushed inwards to a distance of i cm. 

 It is then impregnated with i c.c. of a watery solution of pyro- 

 gallic acid (freshly prepared by adding to one part of water an 



Fig. 28. — Flask arranged for culture of 

 anaerobes which develop gas. 



3 is a trough of mercury into which exit 

 tube dips. 



