210 MASS. EXPERIMENT STATION BULLETIN 187. 



12 per cent.; while in the remaining 34 cases (67 per cent.) there was an in- 

 crease during clarification varying from 2 to 256 per cent, and averaging 41 

 per cent. If the total 51 samples are considered there was an average in- 

 crease of 24 per cent. 



Twenty-seven comparisons were made on samples containing from 100,000 

 to 500,000 bacteria per cubic centimeter in the unclarified milk ; 9 comparisons 

 (33 per cent.) showed a decrease during clarification varying from 2 to 36 per 

 cent, and averaging 12 per cent., while 18 comparisons (67 per cent.) showed 

 increases varying from 3 to 187 per cent, and averaging 43 per cent. Con- 

 sidering all of the samples there was an average increase of 25 per cent. 



Fourteen comparisons were made on samples containing more than 500,000 

 bacteria per cubic centimeter in the unclarified milk; only 3 comparisons 

 (21 per cent.) showed a decrease during clarification, 1 of 5, 1 of 27, and 1 of 

 40 per cent, (averaging 24 per cent.), while 11 comparisons (79 per cent.) 

 showed increases varying from 4 to 102 per cent, and averaging 29 per cent. 

 There was an average increase of IS per cent, when the total 14 samples are 

 considered. 



The number of samples of milk under 100,000 bacteria per cubic centi- 

 meter does not show a larger percentage of decreased counts than the 

 samples between 100,000 and 500,000 bacteria per cubic centimeter; in 

 fact, the milk samples of over 500,000 bacteria showed a less increase than 

 the samples with a lower number of organisms. All the samples were 

 market milk samples; accordingly, the histories of the samples are un- 

 known. This makes it difficult to draw any specific conclusions. 

 Hammer's work is, however, very interesting in connection with the 

 results of this laboratory, which will be furnished later. 



A general critical review of the clarifier tests has been written by Prof. 

 E, G. Hastings for the Journal of the American Medical Association for 

 March 24, 1917. His conclusion intimates that the clarifier may not be 

 a progressive step in the purification of milk. This is a somewhat hasty 

 conclusion without his having investigated the results of its action a 

 little more closely. Too much is superficially apparent in its action to 

 turn it aside with the wave of the hand and the cynical remark, "What 

 next?" An extended acquaintance with the machine and its operations 

 will at least suggest very subtle problems, perhaps much more illuminat- 

 ing if solved than any which have been attacked thus far, and causes one 

 to speculate about milk questions which have been heretofore untouched 

 or remotely surveyed. From time to time these suggestions will be 

 hinted at in the text. 



