1 Jan., 1899.] QUEENSLAND AGRICULTURAL JOURNAL, 27 
udder to prevent dislodgment of dust particles, steaming the pails and cans to 
destroy lurking germ life, rejecting the fore milk, keeping the stable free from 
dust during the milking, are all practical methods that have arational scientific 
asis. 
Where these methods are conscientiously carried out, good results are to 
be obtained with ease. Private dairies, that are engaged in supplying the best 
quality of milk, are following such methods with success. For factory 
purposes, such scrupulous care as is practised in milk dairies would perhaps 
be considered impractical ; but if our factory milk was handled with equally 
great care, the hundreds of thousands of dollars that are annually lost in this 
State alone on inferior dairy products would, for the most part, be saved. 
EFFECT OF CHILLING ON BACTERIAL GROWTH IN MILK. - 
Suppose that the greatest care has been taken to secure the milk in as 
clean a manner as possible. ‘This will reduce the number of bacteria in the 
same proportion, and yet, if no pains are taken to chill it, the advantage gained 
will be largely lost. The temperature of the milk as it comes frum the cow 
approximates blood heat, and, therefore, the conditions are most favourable for 
bacterial growth. At 80 degrees Fahr. a sitgle organism will form 120 new 
individuals in four hours, while the development of the same germ would have 
been so retarded at 50 degrees or 55 degrees Fahr. that but little increase 
would have taken place. 
The secret, then, lies in early cooling. If the milk is allowed to cool 
naturally it loses its animal heat so slowly, especially in a large volume, like a 
canful, that the bacteria that are contained in it are able to multiply ina 
vigorous manner. To check this development, the milk should be cooled as 
soon as possible. An early diminution of the temperature is much more 
efficient in checking growth of germ life than even a longer exposure applied 
later. 
WHY MILK SOURS. 
Tf milk is allowed to stand for several days, it almost invariably under- 
goes a change that is known as souring. Its physical appearance is much 
altered, and the once valuable food is converted into a relatively worthless 
by-product. This change is a fermentative process that goes on in the milk, 
and is caused by a large group of different bacteria. These kinds are particu- 
larly numerous in stables and barns; moreover, they seem to find in milk such 
good surroundings that they grow with great rapidity. 
The sour taste of milk, so fermented, is due to the formation of lactic 
acid, that is produced by the splitting up of the milk sugar in the milk. As 
acid is formed in gradually increasing amounts the chemical reaction changes 
from a neutral to an acid condition. When the amount of acid formed 
approximates 0°6 per cent., the casein is unable to remain in its normal 
condition, and is precipitated, forming the solid curd that is characteristic of a 
sour-milk fermentation, The formation of acid does not go on. until the sugar 
of the milk is all decomposed, for the lactic-acid bacteria are unable to grow 
where the amount of acid exceeds 0°8 per cent. They are retarded, therefore, by 
the presence of their own by-products. 
The souring of milk is so universal a phenomenon that it is considered 
almost a natural and inevitable change in milk, and yet, if milk could be 
secured without bacteria, it would undergo no such change. 
DOES THUNDER SOUR MILK? 
No exception can be taken to the statement that milk is very apt to sour 
during a thunderstorm. This universal experience has led to the notion, 
thoroughly believed by many, that the cause of the souring is due to the action 
of thunder, or possibly the electric discharge. Experimental researches upon 
this question, however, fail to establish any such relationship. The passage of 
the electric spark through milk does not increase the acidity of the same. If 
bacterial growth is held in check in various ways, no atmospheric disturbance, 
