MICROSCOPICAL AND PHYSIOLOGICAL EXAMINATION. 19 



right is quickly withdrawn, and the hot tube of the first 

 flask is introduced into the India-rubber tube of the second 

 flask. The liquid is now poured into the latter flask, the 

 bent tube of the former flask being at the same time 

 heated. Then the side tube of the left flask is again 

 introduced into the flame, while the stopper of the right 

 flask is heated and put back into its place ; finally, the left 

 flask is closed in, the flame with its tube and stopper. 

 When the operation is quickly performed, there is seldom 

 any danger of contamination. 



Pasteur flasks will be found indispensable in certain 



FIG. 4. 

 Chamberland Flask. 



operations ; as, for instance, in physiological researches where 

 one has to deal with large quantities of liquids. 



In recent years various other flasks and vessels have 

 been brought into use, notably the Chamberland flask 

 (Fig. 4), the neck of which is closed with a ground cap, 

 which terminates above in a short, open tube ; this tube 

 is filled with tightly-packed sterilised cotton-wool. 



The Frewdenreich flask is constructed on exactly the 

 same principle ; it has, however, a cylindrical shape. 



For certain special purposes Hansen's flask (Fig. 5) is 

 employed. The ground cap is provided with a cotton- 



