242 



APPLIED BACTERIOLOGY 



thorough examination. To produce these films, Hansen 

 proceeded as follows : Having obtained his pure cultivation, 

 drop cultures were made into four-ounce flasks, half filled 

 with sterilised wort, and protected from falling particles 

 by being covered by a well-fitting cap. The films first 

 appear as small opaque points, which gradually increase 

 in size and then run together, forming irregular patches 

 floating on the upper surface of the liquid. As soon as 

 the film becomes apparent to the naked eye, it is examined. 

 The film at length overspreads the whole surface of the 

 liquid, and becomes adherent to the walls of the flask. A 

 very necessary condition for the formation of films is perfect 

 rest of the liquid in which they are being formed. 



The following tables, compiled by G. H. Morris {J. 8. C. I., 

 1887, p. 119), show the differences exhibited by a number 

 of varieties of yeasts examined by Hansen's methods, with 

 respect to the formation of ascospores and films respec- 

 tively : 



ASCOSPOEE FORMATION. 



