176 BACTERIOLOGY. 



Method of Buohner. The plan suggested by Buehner 

 of allowing the cultures \o develop in an atmosphere 

 robbed of its oxygen by pyrogallic acid gives very good 

 results. In this method the culture, which is either a 

 slant or stab culture in a test-tube, is placed — tube, 

 cotton plug, and all — into a larger tube in the bottom 

 of which has been deposited 1 gramme of pyrogallic 

 acid and 10 c.c. of j^g- normal ' caustic potash solution. 

 The larger tube is then tightly plugged with a rubber 

 stopper. The oxygen is quickly absorbed by the pyro- 

 gallic acid, and the organisms develop in the remaining 

 constituents of the atmosphere — nitrogen, a small 

 amount of COj, and a trace of ammonia. 



Method of C. Frdnkel. Carl Frankel suggests the 

 following as a modification of or substitute for the 

 tubes of Liborius : The tube is first prepared as if for 

 an ordinary Esmarch tube. The cotton plug is then 

 replaced by a rubber stopper, through which pass two 

 glass tubes. These must all have been sterilized in the 

 steam sterilizer before using. On the outer side of the 

 stopper these two tubes are bent at right angles to the 

 long axis of the test-tube into which they are to be 

 placed, and both are slightly drawn out in the gas 

 flame. At the outer extremity of both of these tubes 



1 A normal solution is one that contains in a litre as many grammes of the 

 dissolved substance as are indicated by its molecular equivalent. The equiva- 

 lent is that amount of a chemical compound which possesses tlie same chem- 

 ical value as does one atom of hydrogen. For example : One molecule of 

 hydrochloric acid (HCl) has a molecular weight and also an equivalent 

 weight of 36.5 ; a molecule of this acid has the same chemical value as one 

 atom of hydrogen. Its normal solution is therefore 36.5 grammes to the litre. 

 On the other hand, sulphuric acid (H2SO4) contains In each molecule two 

 replaceable hydrogen atoms ; its normal solution is not, therefore, 80 grammes 

 (its molecular weight) to the litre, but that amount which would be equiva- 

 lent chemically to one hydrogen atom, viz., 40 grammes (one-half its molecu- 

 lar weight) to the litre. A normal solution of caustic potash contains as 

 many grammes to the litre as the number of its molecular weight — 56.1 

 grammes to the litre of water. 



