Foreword 



This edition of the Difco Manual, the ninth published since 1927, has 

 been completely revised and rewritten. The Ninth Edition is the first to 

 include the reagents used in the preparation of media for in vitro propa- 

 gation and maintenance of tissue cells. 



When we first introduced prepared dehydrated culture media to the 

 scientific world, they were regarded as laboratory curiosities. Today, Difco 

 products are used in microbiological laboratories in all parts of the world. 

 Difco products are not only being used by a continually increasing number 

 of investigators, but are also constantly extending into new fields of micro- 

 biology. Bacto Dehydrated Culture Media and laboratory reagents are 

 used in municipal and state health departments, water and sewage works, 

 in dairies, in medical and technical colleges and the larger universities, in 

 private diagnostic laboratories, hospitals, and commercial laboratories. 

 Research laboratories maintained by the Federal Government are also 

 users of Difco products. 



Recommendation and approval have been extended to our products by 

 the authors of many standard textbooks of bacteriology and by the com- 

 mittees on methods and procedures of scientific societies such as the 

 American Public Health Association, the American Dairy Science Associa- 

 tion and others. 



Bacto Dehydrated Culture Media and laboratory reagents are prepared 

 according to available standards or accepted formulae. Each ingredient is 

 thoroughly tested and the final product is subjected to rigid examination 

 and is standardized before being offered for distribution. The new section 

 entitled Tissue Culture Media Reagents describes the products prepared 

 in collaboration with the Tissue Culture Association and are tested and 

 certified for tissue culture procedures. 



The dehydrated media are stable and resist deterioration over long 

 periods of time. They are readily and quickly prepared for use and yield 

 uniform lots of media which provide identical nutritional conditions at all 

 times. Aside from these readily apparent advantages, Bacto Dehydrated 

 Culture Media are truly economical when actual cost comparisons are 

 made. 



Grateful acknowledgment is made of the support we have received 

 from bacteriologists the world over. It is the desire of our organization to 

 continue and to extend our services to the advancement of microbiology 

 and related sciences. 



Difco Laboratories 



