299 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 
Fic. 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- 
