340 EXPERIMENT STATION EECORD, 



The data obtained in connection with the World's Fair test are also 

 tabulated according to the age of the cows. Although there was con- 

 siderable difference in the average time since calving, " the general 

 tendency seems to be toward a slightly increased number of globules 

 per unit of milk with increasing age, and a similar decrease in the 

 average size of the globules." 



The sources of bacterial infection and the relation of the same 

 to the keeping quality of milk, 11. L, Uussell ( Wisvonsrn iSta. Ept. 

 1894, pp. 150-165, figs. 3). — The sources of infection are discussed in a 

 popular way under the heads infection from unclean vessels, from 

 foremilk, fi^om animal and milker, and from the barn air, and some 

 experiments are given bearing on these points. As showing the advan- 

 tage of sterilizing milk vessels with steam, covered milk pails were 

 used, one of which had been cleaned in the ordinarj^ way and the other 

 sterilized with steam for half an hour, TLe udder of the cow was 

 thoroughly washed, the hands of the milker cleaned, and the first por- 

 tion of the milk was rejected. Gelatin cultures of the milk drawn in 

 each pail showed 165 germs per cubic centimeter in the milk from the 

 sterilized pail and 4,205 germs per cubic centimeter in that from the 

 pail cleaned in the ordinary way. The latter soured in 23 hours, while 

 that in the sterilized pail remained sweet 5i hours longer. 



''Numerous repetitious of the same method of procedure ofteu showed still greater 

 difterences, iu some cases there beiug a difference of 15 hours in the leugth of time 

 before the milk hegau to turn. • These experiments were confined entirely to the 

 milking vessels, hut the same influences are at work in connection with all other 

 kinds of dairy utensils. Cans in which the milk is set for creaming, all dippers, and 

 strainers should be rendered as germ free as pos3il)le, so that the number of organ- 

 isms added to the milk will be reduced to a minimum. Under average conditions, 

 it may be confidently asserted that, with this simple precaution alone, the market- 

 able period, t. e., the length of time during which milk remains sweet, may be 

 extended from 6 to 10 hours." 



In another experiment the milk drawn first from each duct was kept 

 separate in a sterile tlask. This was found to contain 2,800 germs per 

 cubic centimeter, while the remainder of the milk averaged only 330 

 germs. 



"The character of the bacteria in each sample presented marked differences; 

 those in theforemilli belonged to a single species of the lactic acid group of organ- 

 isms, while those in the mixed milk were included under several difi'erent forms, the 

 majority of which belonged to the rennet-forming si^ecies that produce such pro- 

 found changes in the character of the milk." 



The cow and the milker are shown to be important sources of infec- 

 tion, and it is recommended that the udder and flank of the cow be 

 well carded and brushed, the udder washed, and the hands of the milker 

 cleaned with soap and warm water immediately preceding milking. 

 "It is also well to have the milker, espe(;ially the upper portion of his 

 body, clothed in an outer garment kept for this purpose." 



Numerous experiments are reported in regard to this matter, the 

 method being to expose a gelatin culture dish underneath the cow at 



