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PUBLIC 

 HEALTH 

 LIBRARY 



PREFACE. 



The object of this work is to trace out the ultimate causes 

 of disease — not of particular diseases — but of disease in 

 general. 



In writing a work of this kind two courses are open to the 

 author. One is to saturate himself with all the available litera- 

 ture on the subject, and, having done so, to connect into an 

 intelligible whole the facts and opinions thus gleaned, adding, 

 amending, and omitting as may seem fit. The other is for 

 him to think the subject out independently from beginning to 

 end, and to draw upon the resources of literature only just so 

 far as apposite matter may chance to present itself in the 

 ordinary course of his reading, or as his line of thought may 

 from time to time suggest some special reference. 



I have adopted the latter course, not, indeed, from any 

 preconceived plan, but rather from the force of circumstances, 

 which led me in the first instance to think out the subjects 

 here treated of for my own personal benefit. 



And, on the whole, I am inclined to think that the second 

 of these two methods is the better ; for, although the author is 

 put to the pains of thinking out for himself questions which 

 have already been decided, and, moreover, runs the risk of 

 being charged with plagiarism, his work is far more likely to 



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