BIOGENESIS AND ABIOGENESIS 115 



fluid was placed had a long neck bent into a zig- 

 zag shape the contents remained untainted by 

 life. The explanation of all these things is very 

 simple, now that we know it. The air all around 

 us is full of minute organisms, such as bacteria, 

 which are capable of growing and multiplying 

 wilh enormous rapidity in various infusions, 

 such, for example, as beef-tea, and, by their 

 growth, of causing the putrefaction of the fluid 

 in question. Hence in all such fluids which 

 have been exposed to the air there are these 

 small organisms and it is only a question of 

 tune as to when the fluid will " go bad " as 

 we commonly put it. Let, however, such a 

 fluid be boiled for long enough and all the 

 organisms which it contains will have been 

 killed and the fluid rendered temporarily sterile. 

 Now if it is again exposed to the air it will 

 again accumulate bacteria and again commence 

 to decompose. Let us suppose, however, that 

 when the process of boiling has gone on for 

 long enough and the fluid is quite sterile, the 

 neck of the flask in which it has been boiling 

 is hermetically sealed up. No further bacteria 

 can obtain admission and the contents will 

 remain " good " as long as the seal of the neck The 

 rem lins perfect. It is on this experiment that 

 the " canning " trade has been built up and 

 every glass jar of soup or of calves'-foot jelly 



