DAIRY FARMING DAIRYING. 293 



requirements relating to market milk in tlu> different States and Territories are also 

 compiled. 



There is some supervision of the milk supply in practically all the cities of the 

 United States having a population of over 50,000, while in the smaller cities and 

 towns supervision is the exception rather than the rule. The methods followed vary 

 widely as well as the character of the work performed. The inspection work con- 

 sists for the most part of testing samples of milk for the content of fat and other 

 solids. So far as the composition of the milk is concerned laws, ordinances, and 

 regulations are considered quite well enforced, but beyond that their enforcement is 

 very imperfect. In the discussion of the information presented in the bulletin many 

 suggestions are made for the improvement of present conditions. 



Economical methods for improving' the keeping qualities of milk, C. F. 

 DoAXE {}[((rij}(ind Sfa. Bid. SS, pp. 117-164). — The author discusses the source of 

 bacteria in milk and practical means for controlling their growth, including in the 

 bulletin the results of considerable original work consisting for the most part of tests 

 of methods in common use. 



Bacteria in milk are derived from the interior of the udder, from the exterior of 

 the cow, from the milker, from the air, and from dairy utensils, nearly all of which 

 sources can be regulated to a certain extent. The value of dampening the udder 

 and flank before milking was shown by bacterial determinations in several trials. 

 In cleansing utensils where steam is not available the author recommends the use of 

 washing powders, the efficiency of this method having been shown in experiments 

 reported in an earlier bulletin of the station. 



In the purification of milk several tests were made with filters and separators. 

 Milk filtered through animal charcoal which had been thoroiighly washed in water 

 was turned black, illustrating a difficulty in purifying milk by filtration as compared 

 with purifying water. The use of separators for purifying milk by 2 city dairies 

 failed to give satisfaction to consumers, the main objection being that milk so treated 

 soured sooner than untreated milk. In 4 out of 5 trials made at the station the 

 acidity of fresh samples of separated milk was found to be higher than that of 

 unseparated samples, the difference in one instance being 0.03 per cent. The cause 

 of this variation was not investigated. It is suggested, however, that it may be due 

 to a change in the content of carbon dioxid, due to the process of separation. The 

 results of the tests indicate that the use of the separator for purifying milk tends to 

 lessen rather than improve its keeping qualities. 



Determinations were made of the number of bacteria and the percentage of acid 

 in aerated and unaerated milk. At the end of 24 hours there was no noticeable dif- 

 ference in the acid content, as shown by 11 trials conducted under ordinary dairy 

 conditions. The development of bacteria was also unaffected to any marked extent 

 by aeration. It is therefore believed that the keeping qualities of milk are not 

 improved by aeration. 



In a series of experiments the effect of cooling milk in different ways was studied. 

 As the temperature of the well water in the State is commonly 60° F, this temper- 

 ature was used as a basis for comi^arison. Milk cooled immediately to 60° was com- 

 pared as regards acidity and germ content with milk cooled gradually by setting in 

 running water at 60°. At the end of 5 hours the milk kept in running water had a 

 temperature of about 64° when it was cooled quickly to 60° and both lots were 

 kept at that temperature. In one of the four trials the milk cooled immediately 

 remained in a condition fit for use 15 hours longer than the milk cooled gradually. 

 In all trials the keeping qualities of the milk were improved by prompt cooling. 



In the second experiment the keeping property of milk cooled immediately to 60° 

 was compared with that of milk in a 5 gal. can set in a half barrel of water at 60°. 

 At tlie end of 15 hours the milk set in standing water had a temperature of QQ to 

 74°, varying with weather conditions. It was then cooled to 60° and kept at that 



