BACTERIA IN OUR DAIRY PRODUCTS. 763 



BACTERIA IN OUR DAIRY PRODUCTS. 



Bt Pkof. H. W. conn. 



THERE have been no discoveries in the last half-century more 

 startling than those which are now accumulating upon the 

 subject of bacteriology. Every one knows to-day that bacteria 

 have a causal connection with certain diseases, and the whole civ- 

 ilized world has been recently agitated over the attempts that are 

 being made to combat their effect in the human system. The study 

 of the relation of these organisms to the animal body seems to be 

 producing a revolution in the study of medicine, or rather perhaps 

 is creating a science of medicine, for medicine of the past can 

 hardly be called a science. 



"We have heard so much of the disease-germs and their evil 

 effects that bacteria are usually looked upon as unmitigated nui- 

 sances. It is a doubtful chance if any knowledge of their benefi- 

 cial effects has passed beyond the reach of the scientist's laboratory 

 and lecture-room. But science has for a long time known that 

 even the bacteria which are not connected with disease are of im- 

 mense significance in the processes of Nature. The non-pathogenic 

 germs were studied long before the pathogenic forms; but the 

 great attraction offered by the study of disease has led the larger 

 number of bacteriologists in this direction. To-day, however, we 

 are beginning to recognize more than ever the great part played 

 by the harmless bacteria, and to find out that their value in the 

 world far outweighs the injury produced by their mischievous 

 relatives. There is hardly a process in Nature which is not in some 

 way connected with bacteria growth. Fermentation, the raising 

 of bread, the formation of vinegar, the germination of seedlings, 

 the growth of plants, the ripening of fertilizers, the decomposition 

 of animal and vegetable bodies by means of which they are again 

 incorporated into the soil, are all to a greater or less extent depend- 

 ent on the growth of micro-organisms, either bacteria or yeasts. 

 Without the agency of these organisms to prepare the soil, plants 

 could not grow, and life would soon disappear. 



There is no one who is not directly or indirectly connected 

 with the dairy industry. The discoveries of the last twenty years, 

 and more especially those of the last five years, have shown that 

 dairy products are in a large measure connected with the growth 

 of microscopic organisms — some dairy processes, indeed, being 

 nothing more than gigantic breeding experiments. Each of the 

 three chief products of the dairy — milk, butter, and cheese — ^has 

 its own definite relations to bacteria growth and each must be 

 considered separately. 



Milk. — The souring of milk is such a universal phenomenon 



