130 



BACTERIOLOGY. 



Fig. 64. — Pasteur's Flask. 



Pastern's Apparatios. — Special forms of tubes, bulbs, and pipettes 

 are employed by the school of Pasteur. The tubes are provided 



with lateral or with 

 curved arms drawn 

 out to a fine point, 

 and with slender 

 necks plugged with 

 cotton-wool. A 

 double form (Pig. 65) 

 shaped like a tuning- 

 fork, each limb with 

 a bent arm, is con- 

 venient for storing 

 sterihsed broth. The 

 sealed end of an arm is nipped off with sterilised forceps, the sterile 

 broth aspirated into each limb, and the arm again sealed in the 

 flame ; a series of such tubes can be 

 arranged upon a rack on the working 

 table. 



Bulbs with a vertical neck drawn out 

 to a fine point, others with a neck bent 

 at an obtuse angle, plugged with cotton- 

 wool, and a lateral curved arm drawn 

 out to a fine point, are also employed. 

 For a description of these various vessels 

 and their special advantages, the woi-ks 



of PasteiTr and Duclaiix must be con- „ , ^ 



Fig. 65.— Pasteue's Double 

 suited. Tpbj,. 



(h) Cultivation of Anaerobic Bacteria. 



To cultivate anaerobic organisms the same media are employed 

 as for aerobic oi-ganisms, but the methods must be modified, or special 

 apparatus used, so that the oxygen in the air may be excluded. 



In the preparation of plate-cultivations, before the film of gelatine 

 has completely hardened it is covered with a sheet of mica, and the 

 edges are sealed with melted paraiiine. By this process the air is not 

 completely excluded, so that only those organisms which are not 

 strictly anaerobic can be grown by this method. Liborius recom- 

 mends boiling a considerable volume of gelatine in a tube, cooling it^ 

 and after thoroughly distributing the organisms in the still liquid jelly, 

 rapidly solidifying it by placing the tube in iced water. By this 



