
108 THE EVOLUTION OF LIFE 
neutralised; then boiled for ten minutes and 
hermetically sealed, is, after two to three days’ exposure 
to a temperature of 30° C., swarming with Bactertum 
terms. Itis, however, to be remarked that a too great 
concentration of the solution hinders the evolution of 
the Bacteria; the volume of the liquid employed 
should therefore not be too small, otherwise the 
boiling for ten minutes will render the solution too 
much concentrated. Perhaps the negative results 
recorded by some experimenters are to be explained 
in this way.” ... 
‘Instead of cheese can be used peptone (0.2 grm. 
to 50 cc.) with the same result. The peptone is 
obtained by digestion of egg albumen with artificial 
gastric juice, subsequently isolated and purified by 
repeated precipitation with alcohol.” 
Huizinga then went on to describe the constitution 
of a liquid prepared from certain saline substances, 
together with grape sugar, which could be used in 
place of the turnip infusion, and which, with the 
addition of peptone, also yielded swarms of Bacteria 
when it was boiled and subsequently guarded from 
contamination. 
Burdon Sanderson, however, in some remarks 
subsequently made (Vature, October 2, 1873) con- 
cerning Huizinga’s experiments, said: ‘The 
substitution of a soluble immediate principle for an 
insoluble mixed product like cheese, and the use of 
a definite solution of sugar and salts are not material 
improvements. The question is not whether the 
germinal matter of Bacteria is present, but whether 
it is destroyed by the process of heating. Con- 
