PREFACE TO THE FIRST EDITION. 



THE present work has been prepared to give the nurse 

 and the beginner an idea as to the nature of microorganisms 

 and their relation to the world's economy, especially in 

 disease. For this reason much technical material has been 

 omitted, especially in the subject of biological differentiation. 

 Emphasis has been laid upon how bacteria pass from indi- 

 vidual to individual, how they enter the body and act when 

 once within, and their manner of exit. Such general informa- 

 tion concerning the character of the disease process has been 

 included as seemed necessary to clarify the nature of the 

 microbe action. Indeed, the subject matter in many places 

 is but elementary bacteriological pathology. During the 

 preparation of the work the author has had in mind a question 

 he has been asked repeatedly: How do bacteria produce 

 disease? That this question is answered as simply and as 

 well as our knowledge of today permits is the author's 

 sincerest hope. 



H.F. 



(vii) 



