PREFATORY NOTE. 



This volume has been prepared as a text-book for veteri- 

 nary students beginning the study of microbiology. It is not 

 exhaustive but rather elementary in character. In its prepa- 

 ration, the purpose has been to point out the place and role 

 of microorganisms in nature; to give the methods for their 

 study and identification; to indicate the relation of certain 

 species to animal diseases; to give a description of the more 

 important species pathogenic for animals; and a brief discus- 

 sion of the reaction of the tissues to microbian invasion and 

 the theories of immunity. Each of these topics has a volumi- 

 nous literature but the undergraduate can familiarize himself 

 with a few of the essential facts and principles only. In 

 recognition of this, the purpose has been to give a few of the 

 more important facts and to explain briefly the essential 

 principles and theories of infection. In order that the volume 

 may be of further aid as a key to the entire subject, numerous 

 references to the literature are given where the student can 

 obtain at first hand the results of original research. Further, 

 a list of text and reference books on the subject is appended. 



This volume is the outgrowth of a lecture course which 

 has accompanied the laboratory work in bacteriology and 

 protozoology. I have endeavored to choose the material that 

 will be of most help to the student of animal diseases and to 

 avoid as much as possible matters of controversy. I wish to 

 acknowledge my indebtedness for assistance derived from the 

 various text books, reports and current literature on this sub- 

 ject. For reading copy and other assistance I wish to thank 

 Drs. S. H. Burnett and C. P. Fitch of this department. 



V. A. M. 



