196 
PROFESSOR TYNDALL ON THE DEPORTMENT AND VITAL 
at the top, and formed there a living layer through which no oxygen could pass to the 
liquid underneath, which, thus surmounted, remained as clear as water. The obser- 
vation of these facts, and many others of a similar bearing, suggested inquiry into the 
effect which the more or less perfect withdrawal of the air from the infusions would have 
upon the development of life. 
A few experiments with an ordinary air-pump were, in the first instance, made. The 
necks of a series of bulbs charged with turnip-infusion were drawn out at the middle to 
a tube of very small diameter. The open end of the neck being connected with the 
air-pump, the bulbs were exhausted. In some cases, to render the removal of the air 
more perfect, hydrogen was admitted into the bulb and was afterwards withdrawn by 
the air-pump. Before they were detached from the pump the bulbs were immersed in 
luke-warm water. They boiled freely, and after a minute’s ebullition the narrowed 
necks were hermetically sealed. The bulbs were then submerged in cold water, which 
was gradually raised to 212° F. and kept boiling for ten minutes; they were afterwards 
removed and placed in a room with a temperature of about 90° Fahr. 
Four bulbs were thus treated in a preliminary experiment on the 7th of March. 
Two of them remain crystal clear to the present hour ; the two others became cloudy, 
but remained entirely free from scum. The cloudiness, I 
may add, was barely perceptible, but it was perfectly distinct 
to the practised eye. 
By such means, however, the removal of the air must 
have been more or less imperfect, and I therefore resorted 
to the far more effective Sprengel pump. To connect them 
with the pump, the bulbs were thrown into the form repre- 
sented in fig. 11. After the neck of the bulb had been 
plugged with cotton-wool it was bent at right angles above 
the plug, and a portion of it was drawn out to a tube of capil- 
lary diameter, represented at o. The end a was connected 
with the Sprengel pump, and after the exhaustion had been 
continued for the required interval, the neck of the bulb 
was sealed at o. 
On the 14th of March three bulbs charged with the 
turnip-infusion, from which the air had been as far as pos- 
sible removed by the ordinary air-pump, were connected 
with the Sprengel, which continued the exhaustion unin- 
terruptedly for three hours. The air dissolved in the liquid 
freely escaped from it at first, and it continued to appear in 
minute bubbles long after the exhaustion had reached a 
considerable degree of perfection. The drawn-out necks of the bulbs being hermetically 
sealed, the infusion within them was maintained as before for ten minutes at the boiling 
temperature. 
