PUTEEFACTION AND INFECTION. 95 



were boiled for only three minutes in an oil-bath, and 

 were sealed, during ebullition, not by a blowpipe, but 

 by the far more effectual spirit-lamp flame. 



Hay. — Four tubes were charged on the date 

 mentioned with a strong infusion, four with a weak 

 infusion. All eight flasks remain to the present hour 

 clear. 



Turnip, — Two kinds of turnip were tried in these 

 first experiments. Two tubes were charged with a 

 strong infusion, and two with ^ „ 



a weak infusion of a sound 

 hard turnip ; while two other 

 pairs of tubes were filled with 

 strong and weak infusions from 

 a soft woolly turnip. All the 

 tubes remain transparent to the 

 present time. Two or three 

 days' exposure to the air of the 

 laboratory sufficed to cloud all 

 these infusions and fill them 

 with life. 



On the 8th of October twenty-one tubes were 

 charged with infusions of the following substances : — 

 Mackerel, beef, eel, oyster, oatmeal, malt, potato. There 

 were three tubes of each infusion. All of them remain 

 to the present hour unchanged. 



I had not previously seen a more beautiful illustra- 

 tion of the dichroitic action which produces the colours 

 of the sky than in the case of the oyster-infusion. With 

 reflected light it presented a beautiful cerulean hue, 

 while it was yellow by transmitted light. This was 

 due to the action of suspended particles which defied 

 alike the power of the microscope and of ordinary fil- 

 tration. At right angles to a transmitted beam the 

 infusion copiously discharged perfectly polarized light. 



