The History of the Subject 19 



Abbe" Lazzaro Spallanzani (1777) filled flasks with organic 

 infusions, sealed their necks, and, after subjecting their con- 

 tents to the temperature of boiling water, placed them under 

 conditions favorable for the development of life, without, 

 however, being able to produce it. Spallanzani's critics, 

 however, objected to his experiment on the ground that air 

 is essential to life, and that in his flasks the air was excluded 

 by the hermetically sealed necks. 



Schulze (1836) set this objection aside by filling a flask 

 only half full of distilled water, to which animal and vege- 

 table matters were added, boiling the contents to destroy 

 the vitality of any organisms which might already exist in 

 them, then sucking daily into the flask a certain amount of 

 air which was passed through a series of bulbs containing 

 concentrated sulphuric acid, in which it was supposed that 

 whatever germs of life the air might contain would be de- 

 stroyed. This flask was kept from May to August ; air was 

 passed through it daily, yet without the development of any 

 infusorial life. 



It must have been a remarkably germ-free atmosphere in 

 which Schulze worked, for, as was shown by those who re- 

 peated his experiment, under the conditions that he regarded 

 as certainly excluding all life, germs can readily enter with 

 the air. 



In 1838 Ehrenberg devised a system of classifying the 

 minute forms of life, a part of which, at least, is still recog- 

 nized at the present time. 



The term "infusorial life" having been used, it is well to 

 remark that during all the early part of their recognized 

 existence the bacteria were regarded as animal organisms 

 and classed among the infusoria. 



Tyndall, stimulated by the work of Pasteur, conclusive- 

 ly proved that the micro-organismal germs were in the 

 dust suspended in the atmosphere, and not ubiquitous in 

 distribution. His experiments were very ingenious and 

 are of much interest. First preparing light wooden cham- 

 bers, with a large glass window in the front and a smaller 

 window in each side, he arranged a series of test-tubes in 

 the bottom, half in and half out of the chamber, and a 

 pipet, working through a rubber diaphragm, in the top, so 

 that when desired the tubes, one by one, could be filled 

 through it. Such chambers were allowed to stand until all 

 the contained dust had settled, and then submitted to an 



