20 



HISTORICAL INTRODUCTION 



accident seemed also to support the second objection, and 

 Spallanzani did not answer it. Though Spallanzani's experi- 

 ments failed to convince his opponents, they led to important 

 practical results, since in Franfois Appert, 1810, applied them 

 to the preserving of fruits, meats, etc., and in a sense started 

 the modern canning industry. 



From Spallanzani to Schultze, there were no further 

 experiments to prove or disprove spontaneous generation. 

 Schultze, in 1836, attempted to meet the second objection to 

 Spallanzani's experiment, i. e., the exclusion of air, by draw- 

 ing air through his boiled infusions, first causing it to bubble 



Fig. 2. — Sohultze's experiment. The set of bulbs next to the face con- 

 tained KOH and the other set concentrated H2SO1. Air was drawn through 

 at frequent intervals from May until August but no growth developed in 

 the boiled infusion. 



through concentrated sulphuric acid to kill the "germs" 

 (Fig. 2). His flasks fortunately showed no growths, but 

 his critics claimed that the strong acid changed the proper- 

 ties of the air so that it would not support life. Schwann, in 

 1837, modified this experiment by drawing the air through 

 a tube heated to destroy the living germs (Fig 3). His 

 experiments were successful but the "spontaneous genera- 

 tion" theorists raised the same objection, i. e., the change 

 in the air by heating. Similar arguments were brought 

 forward, also to the use of cotton plugs as filters by Schroeder 



