694 APPENDIX A 



to at once cool the milk after it has been drawn from the udder, 

 as milk sent in a warm condition from the country dairy farm 

 to a town, on a journey occupying from six to ten hours, is 

 liable to develop lactic fermentation, which destroys the milk 

 for domestic use. There is a germicidal action which at once 

 sets in after milk has been drawn from the cow, and which 

 continues for four or five hours until the weaker bacteria are 

 destroyed, and the stronger forms become predominant. 

 These, as it were, take possession of the milk and produce 

 decomposition which exhibits itself by "souring," either 

 quickly or slowly according to the external temperature. 

 There is only one satisfactory way of dealing with the milk, 

 i.e., cooling to 38 F. as it leaves the cow. If the milk be 

 cooled at once, carried from the dairy farm to a town in a 

 refrigerated waggon, taken without delay from the railway 

 station to the milk depot, and either distributed or placed in 

 cold store, it will arrive in the ordinary household in perfect 

 condition. 



There is the very serious question of the probable presence 

 of pathogenic germs, such as those of tuberculosis^ which may 

 insidiously enter milk through a diseased udder in an other- 

 wise healthy cow. In the present unsettled state of opinion 

 on this question we are bound to assume that tuberculosis is 

 capable of transmission from the bovine to the human sub- 

 ject, and to place this disease before any other as the most 

 dangerous which may be conveyed by milk. There is only 

 one known way by which the milk for domestic use can be 

 rendered innocuous and free from pathogenic germs, and that 

 is by the use of heat. Low temperatures check their multi- 

 plication, but do not destroy them. The result follows that 

 in many places the practice is to pasteurise all the milk. 



Pasteurisation means the heating of the milk by means 

 of a continuous heater to 180 F. (a higher temperature will 

 caramelise the milk sugar, and produce an objectionable 

 taste), or by means of another form of heater for a prolonged 

 period twenty minutes or thereby to 140 F. ; but neither 

 of these means is effective without subsequent cooling. The 

 milk will become tainted if it be not cooled as rapidly as it is 

 heated. Cooling, as the necessary complement of pasteurisa- 

 tion, is essential in modern dairy practice. From the 

 pasteuriser the milk either runs or is pumped over a circular 



