20 INTRODUCTORY HISTORICAL REVIEW 



Pasteur further constructed a peculiarly shaped glass receptacle, 

 known now as the Pasteur bulb, which has a bent and curved neck 

 through which air can freely circulate without, however, introducing 

 microorganisms. In such bulbs meat infusions which had been 

 boiled for several hours did not develop such growths. However, 

 as soon as the neck was broken off, so that microorganisms could 

 fall into the bulb, the fluid would decompose with the appearance of 

 numerous microbes. The question of spontaneous generation was 

 now settled, and it had been shown that microorganisms could not 

 be so formed. In the meantime the cause of alcoholic fermentation 

 of sugar-containing fluids had been discovered. Erxleben, as early 

 as 1818, had made the statement that this fermentation was due to 

 the multiplication and the metabolism of yeast cells. This, how- 

 over, was not proved until about twenty years later by the extensive 

 ebservations and experiments of Cagniard-Latour, Thedor Schwann 

 and F. Kuetzing, who worked on the problem simultaneously. The 

 vegetable nature of yeast cells had also been recognized, and the 

 idea that diseases were due to vegetable and other microorganisms 

 received a new stimulus. Athanasius Kirchner had already expressed 

 this belief in 1659, and it was strongly upheld in the middle of the 

 eighteenth century by Plenciz and Reimarus; the former believing 

 that each infectious disease was due to a specific microorganism. 



These theories had been long forgotten at the beginning of the 

 nineteenth century; but after the saccharomyces, or yeast cells, had 

 been recognized as the cause of fermentation, the microbic theory of 

 disease was again revived, particularly by the celebrated German 

 pathologist and anatomist Henle, who, in 1840, declared himself in 

 favor of this theory. He was cautious enough, however, to state 

 that it was not sufficient to find microorganisms in certain diseases, 

 but that they must always be present in such cases, and further, that 

 they must be shown actually capable of producing the disease. The 

 succeeding years brought observations and discoveries which demon- 

 strated the fact that bacteria are the cause of certain diseases. The 

 anthrax bacillus was seen and later inoculated into animals by 

 Pollander and Davine (1850-60). Rindfleisch, Recklinghausen, 

 Waldeyer, and Klebs saw the pyogenic cocci in pyemia, puerperal 

 sepsis, and wound infections. Robert Koch, in 1876, published his 

 researches on the anthrax bacillus and two years later those on mouse 

 septicemia. Bollinger, in 1878, recognized the significance of the 

 ray fungus. About this time Robert Koch introduced the use of 

 solid culture media foj* the purpose of isolating bacteria and obtain- 

 ing them in pure cultures. In 1882 he published his researches on 

 the tubercle bacillus. Kitasato later showed how to cultivate the 

 anaerobic tetanus bacillus, and somewhat earlier the first disease- 

 producing protozoa had been discovered. Griffith Evans, in 1880, saw 

 in India, in the blood of horses, mules, and camels suffering from 

 surra, a motile microorganism which he described as a spirillum. He 



