GROWTH OF BACTERIA 109 



be destroyed, for if but one be left alive it will require 

 only a few hours for its descendants to become so numer- 

 ous as to be able to accomplish almost anything in the 

 way of chemical destruction. 



Relation of Growth to Temperature. This great power 

 of growth is dependent upon many factors, most promi- 

 nent among which is temperature. Like all living things, 

 bacteria will not grow at the temperature of freezing or 

 below, but will develop .-,-,,, 



at nearly all temperatures ,-j.'.\'.vf''-^-'-'-.'y-'.<V; 



above, some species even -;-M'--'>."'"':-''"v.'!;.il''''.;>'',''v. 



growing at 140.° Certain ^' \i ^^<^:-:'i^'^^'^i^i^'':^''-^/^-: 



species grow best at a '^^'•■r^'-r'-^^^^'^'^'iys^-'y^ 



temperature that is not '^''.'^,':V^'-'^y''^!Wv;.^'.>;';'■V 



much above freezing ; "'-'v;-VW;l''vY-''''-'''o-'''''.''"'' 



others grow best at "K''r :{•,:'.':■" 



higher temperatures. _ „ , ^i ■ n, a- » c 



° ' Fig. 54. Showing the effect of variations 



Most of the common in temperature on bacteria growth, a, 

 household types require a single bacterium ; b, its progeny in 



considerable warmth for '"■^"'yf""; 1^°"'-^ =^' 5°°; c its progeny 



in twenty-four hoursat 70 . 



their proper growth, and 



the warmer the temperature, up to a certain limit, the more 

 rapid their growth. The relation of temperature to the 

 rapidity of multiplication, for common species, is shown 

 by the accompanying figure (Fig. 54). At a is repre- 

 sented a single bacterium ; at (^ is the progeny of this bac- 

 terium when kept twenty-four hours at a temperature of 

 50°, a little above that of the ordinary ice chest ; at c is the 

 progeny of this bacterium kept the same time at 70°, 

 the ordinary temperature of a living room. A glance at 

 the figure will show what an extraordinary influence a few 



