vi MILK AND THE PUBLIC HEALTH 



to disease. While existing knowledge is extensive there are 

 still large gaps to be filled up. 



In Part II., for the benefit of the laboratory worker, the 

 practical bacteriological examination of milk is described. 

 The methods and procedures which may be used have been 

 set out in some detail, as I know of no book in which the 

 bacteriological examination of milk is adequately treated, 

 while it is manifest that the future efficient control of milk 

 must be worked in conjunction with systematic bacteriological 

 examinations. 



In Part III. the administrative side of the subject is dealt 

 with, including an account of the powers and procedures which 

 are at present used, either in general or for special purposes, 

 and consideration of the practical, administrative, and legal 

 alterations which are held to be desirable. 



All authorities on expert evidence in Courts of Law are 

 emphatic that evidence of fact should be kept distinct from 

 deductions and opinions based upon those facts. In a similar 

 way it is desirable that in text-books as far as possible the 

 scientific facts at our disposal should be presented distinctly, 

 and divorced from the legal and administrative action which has 

 resulted or which should result as the logical outcome from 

 them. In this way clarity of vision is obtained. If fact and 

 deduction were always separated many of the ill-devised and 

 unscientifically-founded public health procedures which are 

 from time to time advocated would be avoided. In pursuance 

 of this object Parts I. and III. have been kept as distinct as 

 the intricacies of the subject would permit, even at the risk of 

 some trifling repetition and some measure of cross reference. 



I have to thank a number of friends for valuable reports 

 and scientific papers giving information upon subjects upon 

 which they are recognised authorities. These sources of 



