ATMOSPHERE IN RELATION TO PUTREFACTION AND INFECTION. 
39 
upright on a wooden stand, and cemented to it air-tight. Through 
the stand passed three large test-tubes (shown in the figure) also 
air-tight. To the top of the cylinder was cemented a circular piece of 
wood, the middle of which was occupied by a pipette, passing first 
through india-rubber and then through a stuffing-box, o, of cotton- 
wool moistened by glycerine*. The air wuthin the case was con- 
nected with the air without by means of the open bent tubes a and b. 
In the first experiments made with these cases defects of construc- 
tion were revealed during the boiling of the infusions. But increased 
experience enabled my assistant to render them secure. The float- 
ing matter within the cases having been permitted to subside, into 
four of them, on the 30th of November, infusions of hare, rabbit, 
pheasant, and grouse were introduced. They were boiled in the 
usual way, and abandoned to the air of the case. Outside each case, 
and hung on to it, were three test-tubes of the same size and 
containing the same infusion as that within. 
Examined on Christmas-day, the following were the observed results : — 
Pheasant. — The three interior tubes perfectly limpid ; the three exposed ones turbid 
and covered with Penicillium. 
Grouse.— The same as pheasant. 
Pare. — The same as grouse and pheasant. 
Babbit. — The three interior tubes covered with tufts of particularly beautiful Peni- 
cillium , some of the tufts striking deep into the liquid. In two out of the three tubes, 
moreover, mycelium was flourishing below. All the outer tubes were, as usual, turbid 
and covered with Penicillium. 
Is this, then, a case of spontaneous generation \ Without further evidence no cautious 
worker would draw such a conclusion. Opposed to this isolated instance stand all the 
others mentioned in these pages, and their proper action on the mind is to compel the 
closest scrutiny before accepting this apparent exception as a real one. Subjected to such 
scrutiny, it appeared that of the four shades the one containing the rabbit-infusion, 
and that only, had yielded to the heat of boiling. The shade had been fastened upon 
its slab with plaster and cement, which became so loose during the boiling that the 
steam issued from the chinks. But crannies which could permit steam to escape could 
permit air to enter, and to the presence of such air the appearance of the Penicillium 
was doubtless due. 
I did not, however, rest content with mere inference, but tested the rabbit-infusion 
by placing three fresh tubes of it in one of the firmer cases first described. It was intro- 
duced and boiled on the 5th of January, three other tubes filled with the same boiled 
* In the earlier experiments the india-rubber formed the bottom of the stuffing-box, where particles were 
sometimes detached from it by the motion of the pipette. To prevent this the positions of wool and rubber 
were afterwards reversed. 
Kg. 3. 
