WHY CLEANLINESS IS NECESSARY 125 



simply by splitting in two, thus if one bacillium 

 be present in milk in half an hour it has split into 

 two, and in half an hour these two have again split 

 into other twos, and so it goes on. Cases are on 

 record where this has been done, and thus from one 

 bacillium seventeen million would be produced in 

 twenty-four hours. As has already been mentioned, 

 bacteria require a suitable temperature before they 

 will increase rapidly ; but there are some kinds 

 which have a very remarkable character. Should 

 the medium they are in become too cold or too hot 

 for their ordinary living in, they have the power 

 of forming what are known as " spores." If the 

 milk they are in be frozen they produce these 

 " spores " rapidly, which remain dormant until such 

 time as they can again thrive. Also, all species 

 of bacteria are not affected by great heat, for they 

 also turn into " spores" when the temperature is 

 too high. Ordinary boiling will not kill all species 

 of bacteria, but those that are killed by this means 

 are mostly the kinds which are unable to form 

 spores. Many different diseases have been proved 

 beyond the shadow of a doubt to be due to bacteria 

 or micro-organisms. Typhoid or enteric fever has 

 been found to be due to the typhus bacilli. Cholera 

 is due to a special bacilli, while tuberculosis has 

 also, along with diphtheria, been proved to be due 

 to a micro-organism or bacilli. 



Milk, as has already been remarked, is an ideal 



