PUTEEFACTION AND INFECTION. 97 



The tubes were immersed in groups of six at a 

 time in an oil-bath, boiled for three minutes, and then 

 sealed. 



More than one hundred of these flasks were sensibly 

 transparent and free from turbidity at the outset, and 

 they remain so to the present hour. In some cases, 

 however, it was not possible to wholly remove turbidity 

 Idj filtration. I have already referred to the opalescence 

 of oyster-infusion, which has invariably appeared when- 

 ever oyster has been digested. A still more pronounced 

 case of the kind is furnished by an infusion of the 

 crystalline lens of the ox. Nothing hitherto encountered 

 by me imitates the flush of the true opal so closely as this 

 infusion. Filtration through one hundred layers of paper 

 i^as quite incompetent to remove the suspended particles 

 to which this opalescence is due. Some of the other 

 infusions remained turbid after filtration, without ex- 

 hibiting what I should call opalescence. The sheep's 

 lungs furnish an example of this. In some cases, 

 moreover, where repeated filtering failed to remove the 

 suspended particles, a few weeks' quiet caused them to 

 sink, and leave the supernatant liquid clear. It may 

 be worth remarking that some rabbit-infusions have 

 shown a decided opalescence, while others have been 



H 



