PASTEUR, KOCH, AND OTHERS 285 
life-giving properties? This doubt grew until a reéxamina- 
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, 
Theodor 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 found quite as effectual as sulphuric acid.” 
- Schwann’s apparatus was similar in construction, except 
