EXPERIMENT STATION BULLETINS. 293 



future, this perplexing piobleni may receive some light which will lielp it to a satis- 

 factory solution. At the present time, those who furnish lis our best milks submit 

 them to careful aeration, believing that by this act the quality of milk is greatly 

 improved. The usual methods of aeration are very imperfect. They fail to bring all 

 the ])arts of the milk in contact with tlu» air. therefore a good sliare ot it is not 

 aerated. If aeration is to be complete, an apparatus is necessary which will produce 

 the most perfect film or finest spray, for it cannot be expected that the air will enter 

 very deeply into milk when exposed for only a second or two.. If aeration is as 

 desirable as is generally supposed, the ordinary management of milk must be A^ery 

 imperfect. 



Concerning the importance of cooling milk, there can be no doubt. The warm milk 

 as it comes from tlie cow furnishes a most highly desirable temperature for the 

 development and multiplication of bacteria. In the summer time, several hours are 

 required to cool the milk down to the surrounding temperature, which in turn may of 

 itself be very suitable for the growth of bacteria. Consequently, there is furnished in 

 connection with the milk as food, the most favorable temperature from the time the 

 milk leaves the cow until it is either changed or consumed. In the winter time, eA^en 

 if the atmosphere is very cold, much time is consumed before the warm milk coming 

 from tlie cow is cooled down to such a deuree that tlie multiplication of bacteria is 

 checked. If a sample of milk be taken and divided so that half be placed in a refrigera- 

 tor and the other half at the ordinary room temperature, there will be found a great 

 difference in the rapidity of bacterial multiplication. In the estimation of the number 

 of bacteria in the sample placed in an ordinary refrigerator with a temperature of 60 

 degrees F., and in the sample placed in the room at about 7.5 degrees to 80 degrees 

 F., the writer found that the rate of increase in the room was from fifty to one hundred 

 times greater than in the refrigerator. The cooling of mifk immediately after milking 

 is to a large extent the factor which determines its keeping qualities, for the tem- 

 perature may be reduced to such a low degree that all bacterial development is 

 inhibited, but this should not be interpreted as a cleansing agent, for the bacteria 

 remain alive, although not multiplying, and the filth is still present. It controls 

 but does not eliminate ; it checks but does not destroy. 



What per cent of milk juoducers think it worth while to cool milk? Knowing what 

 it does and how useful it is. so little attention is paid to it in ordinary dairy pursuits 

 that it practically remains an unknown feature in dairy operations. Those milk pro- 

 ducers for whom it would be most useful do not utilize a cooler, and many times when 

 a cooler is used it is maintained in such a filthy condition that it were better to resort 

 to the simple device of the dipper or some apparatus which is easily cleaned. Many 

 object to a cooler that exposes the milk to a very extensive surface because of con- 

 tamination from the air. This, however, is a serious fallacy, for if the room in which 

 the milk is cooled be properly cleaned, this source of infection need not be taken into 

 consideration. .Milk that is cooled over a large surface exposed to the influence of ice 

 is almost instantaneously rendered unfit for germ growth, but following the customs 

 usually employed, a can is first filled, then placed in a vat of cold water, perhaps 

 iced, and stirred until cooled. Too much time elapses in the prosecution of this 

 method, hence it cannot be regarded as the most desirable. Quickness is important 

 in this operation. 



T have already called attention to the necessity of having clean utensils in connection 

 with our discussion of the milk pail. Cleanliness, of course, is the uppermost thought 

 of a successful dairyman's mind, but this does not explain why it has become so 

 generally the practice to make use of milk cans in carrying sour milk and whey from 

 the factory to the stable and then after emptying them, simply rinsing them out with 

 cold water in preparation for the fresh milk. It is not strange under these circum- 

 stances that the milk sours in a few hours' time. It is possible to carry sour milk 

 in a can and clean the can sufficiently, so that it will not have any influence upon the 

 sweet milk introduced. Care, however, will have to be exercised in producing perfect 

 cleanliness. The same may be said of the cooler or the aerator or any milk receptacle. 

 To use a receptacle that is not perfectly cleaned is not only dangerous, but materially 

 reduces the value of the milk. IIow the cleaning should be performed will be described 

 in another place. 



The water sup])ly to a dairy has no little influence upon the keeping qualities of milk 

 and its products. This is true of ice also. Many samples of water and ice have been 

 examined in this laboratory and it has been found that the germ content of either 

 is ca])ab]e of producing a decided eflfect upon dairy products. Some sample dairy 

 waters have been determined to possess several hundred thousand bacteria per c. c. 

 (one-thirtieth of an ounce). Such water as this cannot fail in Yielding unsatis- 



