474 
DR. W. EOBERTS ON BIOGENESIS. 
alkali produce this extraordinary effect? It must be in one of two ways: either it 
increases the vital resistance to heat of the germs contained in the infusion, or it 
increases the abiogenic aptitude of the infusion itself. Which of 
these explanations is the true one ? The question was tested in 
the following manner : — 
Ten flasks were charged with unneutralized hay-infusion. Five 
of these were simply plugged with cotton-wool, and boiled over 
the flame for five minutes. The other five were also plugged 
with cotton- wool; but through the centre of each plug there passed 
a hermetically sealed glass tube, of the shape represented in the 
annexed figure (fig. 6, a b), and containing the proper quantity of 
liquor potassee to neutralize the infusion in the flask. These 
tubes had been previously (after being charged with liquor po- 
tassse and sealed) heated in oil up to 121° Cent., in order to 
destroy any germs they might contain. The flasks thus prepared 
were then also boiled over the flame for five minutes. 
At the end of a fortnight the contents of the ten flasks re- 
mained unchanged ; they were evidently permanently sterilized. 
I next proceeded to alkalize the infusions in the flasks without in- 
troducing any fresh germs, that is, without removing the plugs. 
The flasks of the first set were placed under a bell-jar in company with a beaker 
containing liquor ammoniae. In the course of two hours the volatile alkali had diffused 
through the plugs and had neutralized the infusions, as was evidenced by the formation 
of abundant deposits in them. These flasks were then removed and set aside in a warm 
place to see if they would germinate. 
The flasks of the second set were each treated as follows : — The little tube a b was 
pressed down against the bottom of the flask until it broke at the bend b, then the 
flame of the blowpipe was cautiously directed against the upper end, a. The expansion 
of the contained air thus induced, was sufficient to expel the liquor potassse into the 
liquid below ; immediate turbidity ensued. The flasks were then placed beside their 
companions of the first set. 
Not one of these ten flasks germinated ; at the end of two months they were still 
barren. Now this result was strictly conformable to the view that the effect of the 
alkali was to increase the power of survivance of the germs, but it was wholly uncon- 
formable to the alternative view. According to the former view, the germs contained 
in the infusions were destroyed by the preliminary boiling, and no subsequent addition 
of alkali could, of course, restore their vitality. But on the opposing theory there was 
no reason why the alkali should not have been equally effective in promoting germi- 
nation, whether added before or after the short preliminary boiling*. 
Fig. 6. 
* la fact this was so. It will be remembered that in preparing the hay-infusions they were first made very 
