BACTERIA IN OUR DAIRY PRODUCTS. -jSj 



to it a certainty, and it lias only been by exercising the most 

 extraordinary precautions that scientists have in a few cases 

 succeeded in obtaining milk directly from the cow in such a way 

 as to avoid its becoming contaminated during the milking. At 

 the same time much may be accomplished by cleanliness in the 

 barn and the dairy. The presence of disease-germs in the milk is 

 always to be traced to filth or to carelessness in handling the milk, 

 or to diseased cows. Typhoid-fever germs, for instance, can only 

 get into the milk from some unusual source, and tuberculosis 

 germs only from diseased cows. If it were possible to enforce 

 cleanliness in the barns and dairies, and to obtain sufiicient care 

 in the handling of milk, we should have no more epidemics spread 

 through the milk-supply. But, in the present state of public igno- 

 rance and carelessness as to health, such an enforcement is an 

 impossibility. In our cities and large towns, therefore, the milk- 

 supply must be looked upon as one of the fertile sources for the 

 spread of disease, and it behooves every one to look carefully to 

 the condition of the milk he drinks during times of epidemics, 

 especially of those affecting the digestive organs. 



But even with the most extreme care it is impossible for our 

 milkmen to avoid the presence of the more common forms of 

 micro-organisms which will sour the milk. Recognizing, then, 

 that bacteria are sure to get into the milk, we may next ask if 

 there is no way of destroying them after they get in. If we can 

 kill these bacteria, we can of course preserve the milk longer and 

 render it more healthful. It is easy enough to kill the bacteria 

 though every method is open to certain objections. Various 

 chemicals have been suggested for poisoning the bacteria, or at 

 least for delaying their growth, but they are one and all to be con- 

 demned, as likely to do more harm than good. 



A safer and more effective method for preserving milk is by 

 the use of heat. All bacteria may be killed by heat, and then, if 

 the milk be kept in tightly closed bottles, it will keep sweet indefi- 

 nitely. For this purpose many sterilizing machines have been 

 invented in the last few years, all based upon the same principle, 

 but differing much in detail. In all cases the milk is subjected to 

 a high heat. Most of them simply heat the milk to a boiling 

 temperature by means of steam or boiling water, but a few, by 

 boiling under pressure, contrive to raise the temperature consid- 

 erably above boiling water. Although many forms of apparatus 

 have been devised for simplifying the matter, no apparatus is 

 really needed for sterilization. All that is necessary is to put the 

 milk into bottles and boil it for ten minutes with the mouth of 

 the bottle open, then close the mouth and steam it for ten minutes 

 more. This method of sterilization will not kill all of the bacteria 

 in the milk, but it will kill all the disease-germs which are likely 



