hid Peet tk See Res i 
Tesia, 
1876.] Spontaneous Generation. 419 
been studied, render it simply inevitable that we have at length 
reached, what we are justified in believing to be, a genetic 
product of the bacteria through which their continuation as or- 
ganisms is preserved. When first I saw the simplicity and beauty 
of this method, it struck me that its applicability as a test in 
reference to germs — known to be such — would have consider- 
able collateral weight; and a method of employing it was sug- 
gested by a fact in past experience.! I had in my possession a 
maceration of cod’s head, which I had kept in use for eleven 
‘months. It had become a pulpy mass, and in the middle of Jan- 
uary last it was comparatively free from bacteria, but swarmed 
with two monads — the fourth and sixth of the series described 
by my colleague and myself. To ascertain their exact condition, 
I watched them on the “ continuous stage” for three consecutive 
days, and found that both forms were to be seen plentifully 
emitting spore. The maceration had become very short of moist- 
ure, which served my purpose. I subjected it to a dryer air 
with a higher temperature, and it was not very long in becoming 
a moist pulpy mass, with sufficient cohesiveness to be removed 
from the vessel ; and in this condition it was placed in a heating 
chamber, which was slowly raised to a temperature of 150° Fahr., 
and kept at this for an hour. This was 10° Fahr. higher than 
Dr. Drysdale and myself had proved necessary to destroy abso- 
lately every adult form. The baked mass now appeared cracked, 
porous, and flaky. In parts it was extremely friable, and with 
little pressure crumbled into almost impalpable powder; while 
by friction a very large proportion was reduced to the finest dust. 
+0 avoid all possibility of error this powder was again exposed 
m the heating chamber, spread over a plate of glass, to a temper- 
ature of 140° Fahr. for ten minutes — thus rendering the plea of 
mere desiccation impossible. 
chamber or box was now prepared precisely like Professor 
yndall’s, except that there were no tubes to communicate with 
the outer air. 
In the Researches on the Life-History of Monads we had proved 
3 they could live, thrive, and multiply almost as well in 
a S “nutritive fluid” as in the normal animal infusion. 
i fluid is composed of phosphate of potash, sulphate of mag- 
triple basic phosphate of lime, tartrate of ammonia, and 
"ea Water. If these ingredients are all mingled the fluid 
mes speedily charged with bacteria, unless hermetically 
? Monthly Microscopical Journal, xii. 262, 263. 
