22 



HISTORICAL INTRODUCTION 



Fig. 5. — Pasteur's flask. 



Fig. 6. — Tyndall's box. One side is removed to show the construction. 

 The bent tubes at the top are to permit a free circulation of air into the 

 interior. The window at the back has one corresponding in the front 

 (removed). Through these the beam of light sent through from the lamp 

 at the side was observed. The three tubes received the infusion and were 

 then boiled in an oil bath. The pipette was for filling the tubes. (Popular 

 Science Monthly, April, 1877.) 



