188 BIOLOGY AND TECHNIQUE 



growth of tubes and plates in anaerobic jars. It depends upon the 

 removal of oxygen by the oxidation of hydrogen under the influence 

 of palladinized asbestos wool. Pfuhl had previously used the 

 catalytic action of platinum sponge for anaerobic cultivation in 

 broth tubes. Mclntosh and Fildes adopted and improved upon this 

 method. The principle of the method is to suspend in an air tight 

 jar a bit of asbestos wool impregnated with platinum or, better, 

 with palladium black. Hydrogen is then allowed to pass in until 

 no oxygen remains. We have used this method in our own labora- 

 tory with great success where a number of the workers compared 

 it with other methods, and it has been used successfully at the 

 Rockefeller Institute by Olitsky and others. 



An ordinary museum jar, such as those used for anaerobic work, is the 

 vessel employed. The lid is perforated for the passage of hydrogen, and 

 from the bottom of the lid there is suspended a bit of the impregnated 

 asbestos wool, inclosed in a small cage of copper wire. About 0.25 gram 

 of the asbestos wool is the amount recommended by Mclntosh and Fildes. 



"The palladium asbestos (about 40 per cent) is made by weighing out 

 0.25 gram of asbestos wool, placing it in a small evaporating dish, and 

 adding 1.5 c.c. of a 10 per cent solution of palladium chlorid. The wool 

 is then molded into a flat mass about one inch square, and the dish gently 

 heated until the wool is dry. Since the palladium chlorid is difficult to 

 dissolve, the addition of a little concentrated hydrochloric acid may be neces- 

 sary. The palladium chlorid is then reduced by heating the impregnated 

 wool, first in a smoky gas flame until it is coated with a layer of carbon, 

 and then in a blow-pipe. The palladium asbestos should now be able to 

 light a jet of hydrogen which is made to impinge on it." 



For ordinary purposes the palladium asbestos can be bought. For closure 

 of lids upon the jars, we have used throughout plastocene, the material used 

 by sculptors for molding. 



In using the jars the culture tubes are placed inside the jars and the 

 lid rim and the jar rim are covered with plastocene. The copper gauze, 

 with the asbestos wool, is detached and held over a flame until red hot, and 

 is then rapidly put in place, closing the jar. Through the perforation with 

 proper connections made (best a glass stopper connection) hydrogen is 

 allowed to flow in very slowly, best from a liquid hydrogen cylinder, with 

 careful regulating check valve. It is very necessary to take careful 



the fact that in the absence of oxygen the reducing action of an alkaline solution 

 of dextrose changes the methylene blue to the colorless luecomethylene blue. On 

 exposure to the oxygen of the air, the leucomethylene blue is oxidized back to 

 the colored compound. 



