

THERMAL DEATH-POINTS 57 
three grains of neutral sodium sulphate to an ounce 
of distilled water. When portions of either of these 
fluids are boiled in previously superheated flasks, 
they will continue quite clear for many days, or even 
for weeks. Even when the narrow necks of the 
flasks containing them remain open, these fluids will 
often not become clouded or turbid, and on 
microscopical examination no living Bacteria are to 
be detected therein. | 
Yet, in order to show that such fluids are still 
thoroughly favourable media for the multiplication 
of Bacteria, all that is necessary is to bring either 
of them into contact with a glass rod previously 
dipped into a fluid containing swarms of such 
organisms. In about thirty-six hours after this has 
been done (the temperature being about 80° F.), the 
fluid, which had hitherto remained clear, becomes 
clouded and turbid owing to the rapid growth and 
multiplication of Bacteria—as a microscopical exa- 
mination will reveal. 
Facts of this kind were shown by Burdon Sander- 
-son! to hold good for portions of boiled ‘ Pasteur’s 
solution,” even when freely exposed to the air; and 
I have often verified them with my ammonium tar- 
trate solutions. 
If, however, a freshly prepared infusion of turnip 
is made, and this fluid after filtration is boiled, poured 
into a superheated flask, and left standing side by side 
with the ammonium tartrate solution, at a tempera- 
ture of 80° to 90° F., a remarkable difference between 
1 Thirteenth Report of the Medical Officer of the Privy Council 
(1871), Pp. 59. 
