PREFACE TO THE SECOND EDITION 



The manuscript of the first edition of this book was completed less than 

 three years ago. Since then the subject of antibiotics has made phe- 

 nomenal progress. A number of new substances have been isolated. 

 Several of those known previously as crude preparations have been 

 purified, and some have been crystallized. Penicillin has risen from a 

 metabolic product of certain fungi, promising but difficult to produce, 

 to one of the most important chemotherapeutic agents now available to 

 the medical world, and its yield has been increased a hundredfold by 

 the selection of new strains and by the development of more suitable 

 media and better conditions of growth. Its chemistry has been com- 

 pletely elucidated, and the existence of a number of different forms 

 varying in chemical nature and biological activity has been established. 

 Streptomycin was a laboratory curiosity late in 19435 now it occupies 

 an important place as a promising chemotherapeutic agent for the 

 treatment of certain diseases resistant to penicillin and the sulfa drugs. 

 This rapid progress of our knowledge of the formation, isolation, 

 and utilization of antibiotics makes it advisable to bring out a revised 

 edition of this book. A great deal of new material has been added, but 

 in order to avoid enlarging the book excessively, it was decided to omit 

 a number of references, mostly earlier articles of purely historical in- 

 terest for which the reader is referred to the first edition, and those 

 dealing with the clinical application of penicillin. Several excellent 

 volumes on penicillin dealing with its use for disease control have re- 

 cently been published. 



S. A. W. 

 February 75, 1^4^ 



