INFECTION. 85 



power is always less. Warming the slides, the action of ether and 

 other known reagents will enable one to distinguish them. 



The most difficult of all objects to distinguish from micrococci 

 are fat -globules, or so-called fatty detritus. The difference in refrac- 

 tion is very small, and in mucilaginous solutions the action of re- 

 agents is not always to be depended upon. Cultivation is the only 

 secure course to employ in cases of grave doubt. 



Only mch globules as have the power of multiplication are vital 

 bodies : when this does not take place, we may assure ourselves that 

 we are having to do with some form of pseudobacteria. 



INageli says there are but three diagnostic signs by which we 

 are enabled to recognize, to any degree of certainty, that molecules 

 under our observation are organisms — spontaneous movement, pro- 

 liferation, and equality in dimensions, united with regularity of 

 form. 



The most certain characteristic is movement in a straight or 

 curved line — a phenomenon never to be seen in inorganic mole- 

 cules. 



Multiplication is a character of less importance, because of the 

 liability to adhesion of inorganic or other molecules. Granules, of 

 varying size and of a more or less irregular form, ought not to be 

 considered as belonging to the segmented fungi. 



As to chemical reagents, concentrated acetic acid, which causes 

 all animal tissues to clarify, is without influence on bacteria. Many 

 coloring-stuffs used in microscopic technics are of assistance in diag- 

 nosing bacteria ; among the best of these are hamatoxylin, fuch- 

 sine, and Bismarck brown. 



The Development of Bacteria. 



Of all living organisms known to natural science the bacteria 

 are the most widely dispersed : they may, in fact, be said to be 

 everywhere — in the air, water, upon and in solid animal and vege- 

 table bodies. 



Oeigln. — The origin of all inferior organisms has ever been a 

 question open to most variable and vital discussion ; but, in general, 

 three ways have been assumed for this most important function : 



1. By heterogenesis / that is, by direct production from mineral 

 or organic substances (spontaneous generation). 



2. On the rule that " like begets like " it has been asserted that 

 all bacteria must come from others of the same kind, by one of the 

 recognized forms of generation : fission, spores, etc. 



3. Others assume that, while they derive their origin from 



