178 THE WORLD'S LUMBER ROOM. 



nite time if the air be excluded or filtered through cotton 

 wool, will be found swarming with bacteria in a few days, 

 if exposed to ordinary air. 



There are billions of them in the air of most London 

 rooms and on all exposed surfaces, even on the money which 

 passes from hand to hand. 



When developed they are for the most part colourless 

 and transparent, are constantly dividing and sub-dividing, 

 and exist either singly or joined together in chains. Though 

 in size they vary from the 35oth to the i,oooth part of a 

 millimetre ](one mtllimHrt is less than V tn f an inch) they 

 are exceedingly tenacious of life, like other of the lower 

 organisms, and in the germ state can bear great extremes 

 of temperature without being killed. 



They may be boiled and they may be frozen, and though 

 unable to germinate under these conditions, the life in them 

 will not be extinguished, but, after lying dormant, perhaps 

 for months, they will become active as soon as a favourable 

 opportunity offers. Oil of hops and carbolic acid, however, 

 they cannot withstand. 



Many of the diseases which attack human beings and 

 animals splenic, typhoid, scarlet fevers, &c., have now 

 been clearly traced to the agency of bacteria, and it seems 

 probable that whooping-cough,* measles, chicken-pox, and 

 other infectious disorders, are also the result of their attacks. 

 They increase with extraordinary rapidity, one germ being 

 capable of producing, in twenty-four hours, 16,000,000 

 bacteria, which, when fully developed, can only just be seen 



*The fumes from carbolic acid, sprinkled on a heated shovel, are found 

 to cure whooping-cough very quickly. 



