SPONTANEOUS GENERATION. 17 



heated to redness. While the contents are boiling the steam 

 formed expels the air from the flask ; when the boiling has con- 

 tinued long enough, the heat is withdrawn from beneath the 

 flask, and, as the steam condenses, the air again enters through 

 the iron tube, the red heat of which is kept up, so that all organ- 

 isms contained in the air are burned. In both methods the flask 

 is allowed to cool very slowly in order that the entering air may 

 be as long as possible in passing through the iron tubes, and thus 

 the destruction of its organic matters insured. When cold, the 

 flasks are sealed at ft, figs. A and B, with the blowpipe. 



" In experiments xxix. and xxx., a glass tube filled with as- 

 bestos and platinum sponge was used instead of the iron tube 

 filled with wires. 



" The time during which the infusions were boiled varied, as 

 will be seen by the records, from fifteen minutes to two hours, 

 and the amount of infusion used was from one twentieth to one 

 thirtieth of the whole capacity of the flask, the object being to 

 have the materials exposed to as large a quantity of air as pos- 

 sible. 



" In the account which follows, especial mention is made, in 

 most instances, of the time of the formation of the i film? This 

 is always the first indication which can be had, without opening 

 the flasks, that minute organisms are developed ; it is in fact 

 made up entirely of them, as has been proved by repeated ex- 

 aminations with the microscope. 



"After the flasks were prepared they were suspended from the 

 walls of a sitting-room, near the ceiling, where they were ex- 

 posed to a temperature of between 70 and 80 F. throughout 

 the day and nearly the same during the night. 



" Expt. xii. (B.) * March 13th. The juice of an ounce of beef, 

 to which was added 10 cub. cent.f of urine and 40 c. c. [cubic 



* " The figure [letter] in brackets following the number of the experiment 

 indicates which of the three modes of preparing the experiment was made use of." 



f Cubic centimetres. A centimetre is about equal to ^ of an inch, and there- 

 fore a cubic centimetre is equal to the cube of ^ of an inch, which is ^-5 of a 

 cubic inch. 



2 



