METHODS OF ISOLATION 



101 



Potato. 



Blow on to an ordinary potato-tube below the con- 

 tube B, and plug the latter with wool between two 



b B b, 



Roux's tube. 1. 



striction, a lateral 



constrictions (fig. 92). (These tubes can 

 be bought ready made.) Place a piece 

 of potato in the tube, and sterilize it in 

 the autoclave at 120 C. 



2. Sow the potato in the ordinary way, 

 and then seal the upper end of the tube 

 below the wool plug in the flame (fig. 92). 



3. Attach B to the pump. Exhaust 

 and wash with hydrogen. 



4. Seal the side tube B at the constric- 

 tion b' under a vacuum, and incubate. 



SECTION HI. THE ISOLATION OF 



ANAEROBIC ORGANISMS. 



1. Plate method. 



A. On sheets of glass. The method is 

 similar to that described for aerobic 

 organisms. The technique is difficult 

 but has the advantage that the colonies 



r>nn VIA AYarmnorl nnrlor +lia rmVrn FlG. 92. Roux's tubes for sowing cultures Of 



can be examined under tne micro- anaerobic organisms on potato, 



scope. 



1. (1) Sow three tubes of liquefied sterile gelatin with the organism under investiga- 

 tion, and pour three plates as in isolating aerobes (p. 78). 



(2) Have a vacuum desiccator (previously washed inside with perchloride) at hand, and 

 pour some potassium pyrogallate (p. 89) into the sulphuric acid vessel. A vacuum 

 incubator (p. 104) can also be used. 



(3) Arrange the plates on the shelves as they are poured. 



(4) Lute the bell jar, exhaust, and wash with hydrogen. Disconnect the bell jar by 

 closing the tap connecting it to the pump. 



2. Turro has simplified the method by arranging the plates on glass benches in a large 

 glass dish into the bottom of which some potassium pyrogallate is poured. The ground 

 glass cover of the glass dish is then sealed with paraffin. Agar can be used for the plates, 

 and the whole incubated. 



B. Kitasato's dish. A circular flat glass dish of the size of a Petri dish is fitted 



with two tubes A and B on opposite sides. 

 The tube B is drawn out and sealed. A is 

 plugged with wool (fig. 93). 



This is a satisfactory though fragile and 

 rather expensive piece of apparatus. 



1. Sterilize the apparatus in the hot air 

 sterilizer. 



2. After flaming the end of B, break off the 



point and dip the end into a gelatin tube already sown, and aspirate the medium 

 into the dish through A. Seal B, and let the gelatin solidify. 



3. Attach A to the pump. Exhaust, and wash with hydrogen. Seal A at the 

 constriction a. 



C. Bombicci's apparatus. This vessel is cheaper than Kitasato's. It consists 

 of a circular flat glass dish with a cylindrical appendix of about 10 c.c. capacity. 



1. Pour the medium, agar or gelatin, into the appendix, plug the neck with wool 

 and sterilize in the autoclave. 



2. Select an india-rubber plug with two holes which fits the neck of the dish. Fit it 

 with two tubes as shown in the figure and plug the horizontal limb of each with wool 



FIG. 93. Kitasato's dish. 



