O PRACTICAL DAIRY BACTERIOLOGY 



bacteria. The rapidity with which these bacteria can grow and 

 divide is surprising. In some cases it has been found that 

 under favorable conditions of food and temperature, they may 

 elongate and divide every half hour, and if tney should continue 

 to reproduce at this rate for twenty-four hours it is easily 

 proved that a single bacterium would have by that time about 

 17,000,000 descendants. If each of these should continue to 

 grow at the same rate, each would have, in twenty-four hours 

 more, 17,000,000 descendants, and then the numbers would 

 develop beyond a possibility of appreciation by human mind. 

 It will, of course, be readily recognized that the bacteria do 

 not long continue to multiply at this rate, for, if they did, in 

 a few days there would be no room in the world for anything 

 but bacteria. Their multiplication is constantly being checked 

 by adverse conditions lack of food, lack of moisture, etc. 

 and thus they do not on the whole very materially increase 

 in numbers. But this inconceivable power of multiplication 

 they do possess, and whenever they are placed for a few hours 

 under conditions where they can have plenty of food and mois- 

 ture for growth, they will develop with enormous rapidity, 

 thus producing most profound changes in the substance upon 

 which they are feeding. If they chance to develop in milk, 

 they will cause a variety of changes which it is our purpose 

 to study, for they change its physical and chemical nature 

 profoundly. These changes, due to this enormous possibility 

 of multiplication, have made bacteria of great importance in 

 dairying and elsewhere in nature. 



Production of Spores. There is another method of producing 

 new individuals, an understanding of which is of extreme im- 

 portance in a knowledge of bacteria. It results in the produc- 

 tion of new individuals, although it is hardly a multiplication 

 since one individual only results from one to start with. The 

 phenomenon in question is the production of spores, and it is 

 illustrated in figure 5. The bacterium there figured consists of 



