1184 EXPERIMENT STATION RECORD. 



In the agglutination tests 7 out of 11 milk streptococci reacted with an immune 

 serum in a dilution of 1:10, while 2 reacted in a dilution of 1:400. Eight out of 9 

 streptococci of the pathogenic group gave a positive reaction in a dilution of 1:10 and 

 4 in a dilution of 1:400. The results are interpreted as showing a close relationship 



1 >rt\\ een some of the milk streptococci and pathogenic forms, and this was emphasized 

 by the fact that the milk streptococci which reacted with immune serum in high 

 dilutions were the forms which produced hemolysins. 



The author, therefore, concludes from the results of his own and other investiga- 

 tions, which are cited, that there can no longer be any doubt that pathogenic strepto- 

 cocci are present in milk. How frequently these are present is a question yet to be 

 answered. 



The reduction test as a means of determining- the freshness of milk, P. T. 

 MtiLLEK (Arch. Hyg., 56 (1906), No. 1-2, pp. 108-204, fig*. 5).— In making this test in 

 laboratory work the author uses 4 test tubes, in one of which is put 2 cc. of whole 

 milk and in the others equal quantities of milk diluted with water in the proportion 

 1 :2, 1:4, and 1:8. To each tube is added 0.2 cc. of a 0.2 per cent solution of methy- 

 lene blue, and the liquid after mixing is covered with a layer of liquid paraffin about 



2 cm. in thickness. The samples are then placed in a thermostat at 37° C. and the 

 time required for the reduction of the methylene blue in the whole milk is observed. 



This test was applied to numerous samples of market milk showing different degrees 

 of acidity; mixtures of fresh and sour milk; dirty milk; milk to which soda, boric 

 acid, salicylic acid, formaldehyde, and hydrogen peroxid had been added; and 

 heated milk. 



For fresh milk obtained in a cleanly manner the time required for the reduction 

 of the methylene blue was 10 or more hours, and for milk delivered by producers 

 directly to consumers during cold weather 6 J to 9 hours. The reduction test of milk 

 obtained from small dealers during the forenoons was 5 to 6 hours during cold 

 weather and 1 to 2| hours during warm weather, while that of the samples obtained 

 during the afternoons was f to 3 hours during cold weather and ^ to 1 hour during 

 warm weather. Milk kept at a high temperature showed a shorter reducing period 

 than milk kept at a low temperature. 



Curdled milk reduced the methylene blue in a few minutes. The addition of 

 small quantities of sour milk and also ol manure to fresh milk shortened greatly the 

 reducing period. The neutralization of milk with soda was without influence on its 

 reducing properties, but the addition of soda to milk poor in bacteria lessened the 

 time required for reduction until sufficient acid was produced to render the milk 

 again neutral or acid. 



The addition of preservatives such as boric acid, salicylic acid, and formaldehyde 

 lessened or destroyed the reducing power of the milk. Milk heated for 15 to 30 min- 

 utes at 100° C. showed only a small reducing power, which, however, gradually 

 increased the longer it was kept. 



The author describes a modified form of the laboratory method which he considers 

 suitable for household use in determining the freshness of milk. When reduction 

 does not occur at the end of 1 hour the milk is considered suitable for infant feeding. 



The testing of market milk, A. Lam (Chem. Ztg., 30 (1906), No. 39, p. 467).— 

 This is an abstract of a paper presented before the Sixth International Congress of 

 Applied Chemistry. 



In testing market milk in regard to its sanitary condition the author determines 

 what he calls the catalase number. Ten cc. of milk is treated with 5 cc. of a 1-per 

 cent solution of hydrogen peroxid and allowed to stand for 24 hours at a temperature 

 of 22 to 35° C. The number of cubic centimeters of oxygen gas liberated is desig- 

 nated the catalase number. For fresh pure milk this varies between 0.3 and 1. In 

 cases of mastitis or tuberculosis of the udder this number is found to be increased. 

 Milk showing a catalase number of over 3 is considered unfit for use. 



