Culture Techniques 153 



Summary 



Cultures are maintained either in flasks, tubes, 

 or hanging drops. Most of the preliminary stud- 

 ies, particularly on problems of nutrition, have 

 been carried out in Erlenmeyer flasks. These are 

 large enough to permit a good deal of manipula- 

 tion of cultures and to provide a large volume of 

 nutrient which is only slowly altered by the metab- 

 olism of the tissues. Test tubes require much less 

 space and nutrient but permit only a very limited 

 amount of manipulation. Neither method permits 

 microscopic examination of cultures. A technique 

 for such examination is provided in the various 

 sorts of hanging-drop cultures which are impor- 

 tant for this reason, although they require much 

 more work and do not provide the stable nutrient 

 conditions necessary for satisfactory study of 

 nutritional problems. Since each of these three 

 techniques has its own special advantages for par- 

 ticular types of problem, the best technique for 

 any given problem will have to be chosen with 

 these characteristics in mind. 



