vi Preface 



A knowledge of the new science early became so 

 indispensable for the sanitary expert that a special 

 course in the Bacteriology of Water and Sewage has for 

 some years been given to students of biology and sani- 

 tary engineering in the Biological Department of the 

 Massachusetts Institute of Technology. For workers in 

 this course the present volume has been especially 

 prepared, and it is fitting, we think, that such a manual 

 should proceed from an institution whose faculty, gradu- 

 ates, and students have had a large share in shaping the 

 science and art of which it treats. We shall be grati- 

 fied, however, if its field of usefulness extends to those 

 following similar courses in other institutions, or occupied 

 professionally in sanitary work. 



The treatment of the subject in the many treatises on 

 General Bacteriology and Medical Bacteriology is neither 

 special enough nor full enough for modern needs. The 

 classic work of Grace and Percy Frankland is now ten 

 years old; and even Horrocks' valuable " Bacteriological 

 Examination of Water " requires to be supplemented by 

 an account of the developments in quantitative analysis 

 which have taken place on this side of the Atlantic. 



It is for us a matter of pride that Water Bacteriology 

 owes much of its value, both in exactness of method 

 and in common-sense interpretation, to American sani- 

 tarians. The English have contributed researches of the 

 greatest importance on the significance of certain intes- 

 tinal bacteria; but with this exception the best work 



