66 THE STORY OF GERM LIFE. 



refrigerators. It is their presence, again, that 

 forces us to smoke hams, to salt mackerel, to dry 

 fish or other meats, to keep pork in brine, and to 

 introduce numerous other details in the methods 

 of food preparation and preservation. 



CHAPTER III. 



RELATION OF BACTERIA TO THE DAIRY 

 INDUSTRY. 



DAIRYING is one of the most primitive of our 

 industries. From the very earliest period, ever 

 since man began to keep domestic cattle, he has 

 been familiar with dairying. During these many 

 centuries certain methods of procedure have 

 been developed which produce desired results. 

 These methods, however, have been devised sim- 

 ply from the accumulation of experience, with 

 very little knowledge as to the 'reasons underly- 

 ing them. The methods of past centuries are, 

 however, ceasing to be satisfactory. The ad- 

 vance of our civilization during the last half 

 century has seen a marked expansion in the ex- 

 tent of the dairy industry. With this expansion 

 has appeared the necessity for new methods, and 

 dairymen have for years been looking for them. 

 The last few years have been teaching us that 

 the new methods are to be found along the line 

 of the application of the discoveries of modern 

 bacteriology. We have been learning that the 

 dairyman is more closely related to bacteria and 

 their activities than almost any other class of 

 persons. Modern dairying, apart from the mat- 



