158 MASS. EXPERIMENT STATION BULLETIN 187. 



designed to meet a specific demand which had been fostered by the fre- 

 quent use of another device (the separator) for clarification. 



On the other hand, criticism could be easily framed from a re\aew of 

 literature of manufacturing firms which has for its purpose the setting 

 forth of the merits of the clarifier. Wliile the specific statements have 

 a modicum of truth and a basis in fact, the reader is left to deduce a 

 quantitative estimate which is very misleading. There exists a sinister 

 purpose beneath the surface which is not commendable. How, for in- 

 stance, is the reader to gather the significance of a photograph of slime 

 deposit when he knows nothing about its relation to the milk? Is he to 

 infer that milk which may be highly infectious to man is rendered safe 

 when passed through a clarifier? Such a statement and many others, by 

 inference, are highly reprehensible, and should not be tolerated by in- 

 telhgent men. If the clarifier cannot prove its value per se, then it is rightly 

 questioned and should be weighed in the balance of exacting scrutiny. 

 Let this new contribution be judged by its work stated in concrete and 

 sane speech. It is only fair to the public to have sanitarians and manu- 

 facturers alike deal frankly and honestly with such matters as clarification. 



Such statements need study, and some of them should not have been 

 written before a careful investigation had been made. 



Clarification aims to assist in the purification of milk. Does it do it 

 or does it not, and to what degree? This is the definite goal toward which 

 the work of this laboratory has been directed. At the start it is frankly 

 allowed that the best way to secure pure milk is to have a sound cow and 

 obtain the milk free from dirt and disease contamination. This is a 

 recommendation difficult to execute. Human knowledge and performance 

 are weak. It seems impracticable to many minds. The clarifier is 

 offered as a means to assist in accomplishing what man as a machine fails 

 to do. The performance of the clarifier is bound up in what is re- 

 moved in the slime, and in how the removal of this slime affects the milk 

 from which it has been eliminated. 



II. SLIME. 



Slime is that material which is removed from the milk during the process 

 of clarification, and which adheres to the bowl of the clarifier. It consists, 

 speaking in a general manner, of the so-called leucocytes or epithelial 

 cells of milk, or corpuscular elements of milk, so-called fibrin which exists 

 in milk in the form of microscopic shreds, traces of casein, traces of fat, 

 traces of milk sugar, inflammatory products such as garget at times, 

 bacteria, yeasts, molds which succeed in entering the milk, and the in- 

 soluble dirt which may be present in the milk, or other foreign insoluble 

 particles which may find their way into the milk, — in short, anything 

 which may be suspended and not in solution in milk and which will respond 

 to centrifugaHzation.' 



I A clarifier is a centrifuge, accordingly these terms are employed interchangeably as well as 

 centrifugalization and clarification. 



