VI] GENERAL CHARACTERS OF BACTERIA 97 



solids and fluids, as exudations, water, cultures, tissues, &c., 

 can be successfully employed. 



Growth and Division?- — The rapidity with which bacteria 

 grow and multiply is subject to very great variations, and 

 cateris paribus constitutes definite and characteristic pecu- 

 liarities ; that is to say, some species under the same 

 conditions of soil, temperature, &c., show a more rapid 

 growth and multiplication than others, these bearing no 

 relation to any known condition. Thus of the staphy- 

 lococcus aureus and the streptococcus pyogenes, growing 

 under exactly the same conditions, and on good nutritive 

 media, the former shows incomparably greater rapidity in 

 multiplication, and produces much more copious growth in 

 a given time than the latter ; or if the bacillus of swine 

 erysipelas and the bacillus of swine fever be taken, the 

 latter is found to grow much more rapidly than the former ; 

 and, again, bacillus subtilis and Tinkler's spirillum grow 

 very much faster than bacillus anthracis and cholera spirillum 

 respectively. 



Comparative experiments which the writer has made with 

 a number of microbes as to the rapidity of multiplication, 

 by way of observing them directly under the microscope in 

 a drop of solidified nutrient gelatine at 22° C. (" suspended 

 solid drop ") show as the average of several observations — 



(ff) The streptococcus pyogenes. Complete division of 

 the cocci took place in thirty minutes. 



(^) The staphylococcus aureus liquescens in twenty 

 minutes. 



(c) The streptococcus of erysipelas in forty-five minutes. 



{d) An orange coloured non-liquefying micrococcus in 

 forty minutes. 



' From Klein's article ' ' Infectious Diseases " in Stevenson and 

 Murphy's Treatise on Hygiene, &c., vol. ii., pp. 19-23. 



H 



