278 EXPERIHIENT STATION RECORD. [Vol. 41 



Control of bacteria in milking machines, F. H. Hall {New York State Sta. 

 Bid. Jf50, popular ed. (1918), pp. .3-J5. fig. 1). — This is a papular edition of the 

 above. 



Clarification of milk, I, C. E. Maeshall, E. G. Hooi> et al. {Massachusetts 

 Sta. Bui. 1S7 {1018}. pp. 151-2^2, figs. 10).— The amount and nature of clarifier 

 slime and tlie immediate effect of clarification upon milk are the topics con- 

 sidered. 



A section on.tlie clarification of certified millv by tlie late E. L. Da vies, an 

 officer in the Canadian Army, is included. It records the percentage of slime 

 secured in 440 tests of the milk of 74 cows, together with the breed and age of 

 the cow and the stage of lactation. Tlie average slime percentage was 0.0G7. 

 In 16.8 per cent of the tests the slime percentage was 0.1 or over. In 14.7 per 

 cent of the cases the slime was bloody. 



The authors add to these data a number of other determinations, showing 

 particularly that increased temperature and increased time of holding (result- 

 ing in greater acidity) tend to increase the amount of slime (dry weight) from 

 a unit amount of milk, and comment as follows: "The amount of slime differs 

 widely when secured from the milk of the same cow, from milk of different 

 individual cows, and from mixed milks, whether the mixed milks have the 

 same origin or not. It is also manifest from the work of this laboratory that 

 samples from the same milk when clarified under the same conditions yield 

 practically the same amount of slime. It follows, therefore, that the causes 

 for these variations must be found in the condition of the animal, the condi- 

 tions which surround the manipulation of the milk, and the conditions which 

 are involved in the clarification. From Lieut. Davies's investigations it seems 

 clear that with the beginning of the period of lactation there is a great 

 increase of slime. This may be attributable to the colostral milk, in which 

 colostral cells are numerous. Evidence also seems to point directly to inflam- 

 matory conditions of the udder as a cause of increase ; garget and other prod- 

 ucts of inflammation and germ action within the udder are common, probably 

 much more so than is usually recognized." 



The slime was found to be composed of insoluble dirt, bacteria, leucocytes 

 .("so-called"), fibrin ("so-called"), and any garget discharge present in the 

 milk. A number of quantitative determinations of the bacteria and leucocytes 

 are recorded. The clarifier was found more efficacious in the removal of in- 

 soluble dirt than the cotton filters used in the Wisconsin sediment test. Some 

 observations are included as to the solubility of manure and stable dirt in 

 water and milk. It is held that the reduction, if any, in the nutritive value of 

 milk as the result of clarification may be disregarded. 



The leucocyte counts before and after clarification are tabulated for 25 sam- 

 ples of certified milk and 6 samples of commercial milk, and bacterial counts 

 for 37 certified and 15 commercial milk samples, while several similar series of 

 counts are assembled from the literature. In about 70 per cent of the tests of 

 fresh certified milk clarification effected a reduction in bacterial content as 

 shown by plating methods. Milk held before clarification seemed to increase 

 its bacterial count by clarification to an extent more or less proportional to the 

 length of holding. These results are thought to indicate that fresh certified 

 milk is relatively free from clumps of bacteria, whereas clumping takes 

 place in held milk. The disruption of clumps through clarification is consid- 

 ered the cause of the increased counts. Only 10 or 15 per cent of the market 

 milk samples showed decrease in bacterial counts after clarification, an indica- 

 tion of extensive clumping. 



Ten graphs are given comparing cultures of clarified milk, unclarlfied milk, 

 and clarified milk plus slime with respect to the nunilter of colonics visible 



