2 HISTORY OF MICROBIOLOGY. 



The important role : tbat the compound microscope has played in 

 microbiology calls for something regarding the invention of this instrument 

 an invention which antedates Leeuwenhoek's discovery by nearly 100 

 years. 



The first compound microscope was made by Hans Jansen and his 

 son Zaccharias, in 1590, at Middelburg, in Holland. The instrument 

 was composed of two lenses mounted in tubes of iron; a representation 

 of it, made from the original and still kept at Middelburg, is shown 

 in Fig. i. From that date the microscope gradually improved. In 

 1844 the immersion lens was introduced by Dolland. In 1870 Abbe 

 brought out the substage condenser, which still bears his name. Apo- 



I 



FIG. i. Longitudinal section of a compound microscope made by Zachatias 

 Jansen (1590). a, microscope tube; 6, objective tube; c, ocular. 



chromatic lenses and many minor improvements were introduced by the 

 firm of Zeiss about 1880. 



In 1786 O. F. Miiller (a Dane) first attempted to classify, according 

 to the Linnean system, the various organisms previously discovered, and 

 characterized four or five genera among them, the genus Vibrio, in 

 which, under the terms bacillus, lineola, and spirillum, we recognize forms 

 that correspond with our "bacteria." 



From the middle of the eighteenth century until well on into the nine- 

 teenth, the history of bacteriology is largely the story of a controversy 

 between those who believed that minute living organisms, such as those 

 above referred to, were produced from inanimate substances, and that 

 their formation was spontaneous. Philosophers, poets, and common 

 people of the most enlightened nations accepted this doctrine down to the 

 eighteenth century. The hypothesis regarding formation was known as 

 that of "spontaneous generation," "heterogenesis," and "abiogenesis." 

 The opponents of this theory denied the possibility of a transition from a 

 lifeless to a living condition, and contended that all life came from pre- 

 existing life a theory aphoristically summed up in the phrase " omne 

 vivum ex vivo." Such was the doctrine of Biogenesis, life only from life. 



In 1668, Francisco Redi, an Italian, distinguished alike as scholar, 



