THE HISTORY OF BACTERIOLOGY. 69 



of a herb or an oak, of a worm or a whale, the work is 

 exclusively done by iniinitely small organisms. ' They are 

 the important, almost the only', agents of universal hygiene ; 

 they clear away more quickly than the dogs of Constantinople 

 or the wild beasts of the desert, the remains of all that has 

 had life ; they protect the living against the dead ; they do 

 more : if there are still living beings, if, since the hundreds 

 of centuries the world has been inhabited, life continues, it 

 is to them we owe it." Without them the surface of the 

 earth would be covered with dead organic matter, the 

 remains of plant and animal bodies, which, retaining the 

 elements necessary for the building up of new plant-life 

 and animal bodies, would soon cut off the food supply of 

 new plants and animals ; life would be impossible because 

 the work of death would be incomplete, or, as Pasteur puts 

 it, "because the return to the atmosphere and to the 

 mineral kingdom of all that which has ceased to live would 

 be totally suspended." From his experiments on fermenta- 

 tion and putrefaction Pasteur, by a very natural transition, 

 turned his attention to the diseases of wine, and then to 

 those of the silkworm — diseases that specially affected two 

 important French industries. After most careful research 

 he found that the acetic fermentation, viscosity, bitterness 

 and turning flat of wines, were all due to the action of 

 certain organized ferments, most of which he was able to 

 isolate and study. 



The acid fermentation, he found, was produced by the mycoderma aceti, 

 which consists of short rod-like forms, about double as long as broad, 

 slightly constricted in the middle ; these individual elements, being joined 

 together in long chains, which, as they grow on the surface of the wine, 

 interlace with one another and form a regular film or skin. The bitterness, 

 of wine he ascribed to the presence and action <Sf branched tortuous 

 filaments of about l-Sft to 4jit in diameter, these chains * having a 

 peculiar knotted appearance. The turning flat of wine was due to the 

 presence of delicate unbranched filaments about iji in diameter, which 

 under certain conditions are broken up into short segments which some- 

 what resemble the bacilli met with in a lactic acid fermentation. The 

 cause of the viscosity of wrine was an organism made up of cocci about 

 i.2;u in diameter, often arranged in chains of considerable length. He 

 found, indeed, that the relations of cause and effect were invariable ; wher- 

 ever certain forms were present in addition to the yeasts, or were intro- 

 duced after the yeasts, the result was a special fermentation superadded to 

 the wine fermentation. 



The genius who had shed such a flood of light on the 



