2 THE THEOKY OF SPONTANEOUS GENERATION. 



for the present, we assume as standing without the pale of the 

 term " fermentation," but which, nevertheless, should actually be 

 included therein. Such processes are, inter alia, the transfor- 

 mation of ammonia into nitric acid, occurring in the soil of our 

 fields ; the decomposition and dissolution. of dead vegetable matter; 

 the ripening of cheese ; the formation of bog (iron) ore, &c. &c. 



2. Discovery of Fermentative Organisms. 



The organisms taking part in the processes of fermentation are 

 so minute that only a few can be detected, and that very im- 

 perfectly, by the unassisted eye. The term microbe, introduced 

 into the vocabulary of science by C. SEDILLOT (I.) 1 in 1878, 

 belongs to them of right. Their examination could not be carried 

 on anterior to the invention of appliances for observing minute 

 bodies under high powers of magnification, and therefore the 

 inventors of the microscope deserve to be held in grateful re- 

 membrance in the domain of fermentation. These were Hans 

 and Zacharias Janssen, father and son, spectacle-grinders, of 

 Middelburg, in Holland, who, about the year 1590, constructed 

 a combination of lenses which, although, of course, very imperfect 

 when compared with the instrument of the present day, must be 

 regarded as the first compound microscope made. 



Nevertheless, however great this step undoubtedly was, both 

 from a theoretical and practical point of view, and however fruitful 

 it proved in results, seeing that it rendered possible later dis- 

 coveries in the world of the "infinitely little," and especially of 

 the fermentative organisms ; still the fact remains that the first 

 fundamental observations were made, not with the compound, but 

 with the simple microscope, which then, as now, was little more 

 than a magnifying glass or bi-convex glass lens. 



The honour of having discovered the presence of extremely 

 small and hitherto undetected organisms in putrescent and fer- 

 menting liquids, belongs to another native of Holland, by name 

 ANTONY VAN LEEUWENHOEK. Born at Delft in 1632, he ac- 

 quired during his apprenticeship to a linen or cloth merchant in 

 Amsterdam some skill in grinding small glass lenses. Of this 

 skill he made further use after his final return to his native town, 

 and succeeded in producing lenses capable of magnifying from 40 

 to 100, and even to 150 times. With these he examined various 

 minute objects, and frequently, amongst others, all kinds of 

 vegetable infusions in a state of decomposition. He discovered 

 therein sundry extremely small creatures, many of them capable 

 of motion, which he therefore regarded as animals, and named 

 from their habitat infusoria. He died in 1723. The modern 



1 The Roman numerals given in brackets after the names of investigators 

 refer to the Bibliographical References forming an appendix to the second 

 volume. 



