iv PREFACE 



at present, seem suitable for popular treatment. In 

 my opinion, a knowledge of the well established facts 

 in this field of investigation should constitute an es- 

 sential part of a liberal education ; and the diffusion 

 of such knowledge cannot fail to promote the sanitary 

 interests of the people. 



The general statement may be made that all infec- 

 tious diseases are preventable diseases, and at the 

 present time it is possible to indicate the necessary 

 measures of prevention for nearly all of these dis- 

 eases. That they continue to prevail, and to claim 

 hundreds of thousands of victims annually, is largely 

 due to the fact that the public, generally, has not yet 

 been educated upon these subjects. 



It would seem that so important a matter should 

 receive special attention in our high schools and col- 

 leges, and the writer hopes that this volume may, to 

 some extent at least, serve as a text-book, suitable 

 for the use of students, and as a manual of ready 

 reference for those who are responsible for the sani- 

 tary welfare of the inmates of homes, schools, public 

 institutions, etc. In Part Second the most important 

 infectious diseases are considered in special chapters, 

 and an attempt has been made to indicate the manner 

 in which each one is propagated, its importance as a 

 factor in our mortality statistics, and the best methods 

 of restricting its extension. I have been strongly 



