DAIRY FARMING- — DAIRYING AGROTECHNY. 275 



contains more than 1 part of proteins for 1.2 parts of fat is made from skimmed 

 milli. 



The reducing properties of milk, P. Sommerfeld (Hyg. ZenthL, Jf (1908), 

 No. 1, pp. 1, 2). — From tests with tlie use of a 0.5 per cent solution of neutral 

 red in sterile water the author concludes that the reducing properties of milk 

 are not due to preformed reducing ferments but are of bacterial nature. 



Bacteria in milk, L. A. Rogers ( [/. )S'. Dcpt. Agr. Yearbook 1907, pp. 179-196, 

 figs. 6). — Bacteria in milk, milk flavors, souring of milk, sweet curdling and 

 digestion, bitter milk, stringy or ropy milk, disease-producing bacteria in milk, 

 care and handling of milk, and related questions are discussed in this general 

 summary of micro-organisms in relation to milk. 



" While bacteria are in no way essential to milk, they may be considered as 

 normally present in milk, cream, ice cream, butter, and cheese. They may even 

 occur in milk or its products in very large uHmbers without making it an unsafe 

 food or in any way decreasing its food value. 



" Bacteria known to produce disease are seldom isolated from or counted in 

 milk, iind bacteriological counts should be taken merely as an indication of the 

 way in which milk has been collecte<l or the temperature at which it has been 

 held. High numbers usually indicate insanitary conditions, careless handling, or 

 old milk. However, milk may be collected under very poor conditions and the 

 bacterial count held down by a libei'al use of ice. On the other hand, milk col- 

 lected in the most sanitary manner may in a few hours contain a large number 

 of bacteria if it is held at a high temperature. Low counts may be due not to 

 clean stables and low temperatures, but to the use of antiseptics. 



" Every effort should be made by legitimate means to secure milk with a 

 small number of bacteria, but milk or foods made from milk should not be indis- 

 criminately condemned because they sometimes contain bacteria in numbers 

 which are startling to those not familiar with the nature of these indispensable 

 plants." 



Bacterial associations in the souring of milk, C. E. Marshall and Belle 

 Farrand (Mich. Sta. Spec. Bui. Ji2, pp. 3-63). — Studies were made of the entire 

 microbial content of a number of samples of milk in continuation of earlier 

 work (E. S. R., 17, p. 490), in which investigations were confined to selected 

 mici'o-organisms. " In this work, the micro-organisms isolated from a definite 

 sample of milk are employed for purposes of association with the lactic micro- 

 organism also isolated from the same sample." 



The conclusions drawn from the investigations follow : 



'* Bacteria, ordinarily found in milk, may or may not facilitate the growth of 

 lactic micro-oi'ganlsms. 



"About 57 per cent of the associate micro-organisms when grown in combina- 

 tion with the specific lactic micro-organisms accelerate their growth and action. 



" The relative number of each micro-organism introduced into the combination 

 may or may not have a decided influence upon the acceleration of the growth of 

 tlie lactic micro-organisms of lactic fermentation. 



"Acceleration may occur at the beginning of the fermentation, or at the end. 

 or at any stage between. 



"The means by which this acceleration of lactic fermentation is produced is 

 not the same in all cases. It appears to be due to products manufactin-ed by 

 the associate micro-organisms, sometimes stable to heat, sometimes unstable; 

 sometimes under alkalme conditions, sometimes under acid conditions; some- 

 times with apparent digestion, sometimes with no apparent digestion. 



