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BIOLOGY AND ITS MAKERS 



He devised a box, or chamber, as shown in Fig. 91, 

 having in front a large glass window, two small glass win- 

 dows on the ends, and in the back a little air-tight trap-door. 

 Through the bottom of this box he had fitted ordinary test 



Fig. 91. — Apparatus of Tyndall for Experimenting on Spontaneous 



Generation. 



tubes of the chemist, with an air-tight surrounding, and on 

 the top he had inserted some coiled glass tubes, which were 

 open at both ends and allowed the passage of air in and out 

 of the box through the tortuous passage. In the middle 

 of the top of the box was a round piece of rubber. When 

 he perforated this with a pinhole the elasticity of the rub- 



