PASTEUR, KOCH, AND OTHERS 285 



life-giving properties? This doubt grew until a reexamina- 

 tion of the question of spontaneous generation became nec- 

 essary under conditions in which the nutrient fluids were 

 made accessible to the outside air. 



In 1836 Franz Schulze, and, in the following year, 

 Thcodor Schwann, devised experiments to test the question 

 on this new basis. Schwann is known to us as the founder of 

 the cell-theory, but we must not confuse Schulze with Max 

 Schultze, who established the protoplasm doctrine. In the 

 experiments of Schulze, a flask was arranged containing 

 nutrient fluids, with a large cork perforated and closely fitted 

 with bent glass tubes connected on one side with a series of 

 bulbs in which were placed sulphuric acid and other chemical 

 substances. An aspirator was attached to the other end of 

 this system, and air from the outside was sucked into the 

 flask, passing on its way through the bulbs containing the 

 chemical substances. The purpose of this was to remove 

 the floating germs that exist in the air, while the air itself 

 was shown, through other experiments by Schwann, to re- 

 main unchanged. 



Tyndall says in reference to these experiments: "Here 

 again the success of Schulze was due to his working in 

 comparatively pure air, but even in such air his experiment 

 is a risky one. Germs will pass unwetted and unscathed 

 through sulphuric acid unless the most special care is taken 

 to detain them. I have repeatedly failed, by repeating 

 Schulze's experiments, to obtain his results. Others have 

 failed likewise. The air passes in bubbles through the 

 bulbs, and to render the method secure, the passage of the 

 air must be so slow as to cause the whole of its floating 

 matter, even to the very core of each bubble, to touch the 

 surrounding fluid. But if this precaution be observed water 

 will be jound quite as effectual as sulphuric acid." 



Schwann's apparatus was similar in construction, except 



