1872.] Notices of Books. 495 
those of Mantegazza. He insists, with a great probability, that 
if these were derived from germs pre-existing in the fluid, such 
germs must have been invisible under a power magnifying 1000 
diameters. The dilemma, as regards the origin of bacteria, 
therefore remains—‘ Either they have been developed from a 
multitude of pretty evenly disseminated invisible germs, or they 
have been produced in the fluid by a process of Archebiosis.”— 
(P. 297). Considering the extreme minuteness of bacteria 
themselves, it is surely not contrary to reason to suppose that 
their germs are so minute as to be diffused through a fluid 
without betraying their presence to the vision. Is it not as pro- 
bable that they should be undetected, just as the particles of a 
salt in solution are undetectable by the microscope? But Dr. 
Bastian asks—What is the medium whereby such possible germs 
could possibly be transmitted? He does not discern, with 
Shelley, that— 
‘“ Those viewless beings, 
Whose mansion is the smallest particle 
Of the impassive atmosphere, 
Live like man.” 
It is clear that the germs of fungi, as well as other vegetable 
seeds, are transmitted by the air. As regards bacteria, however, 
it has been clearly proved, by Prof. Burdon Sanderson, that the 
great vehicle for their diffusion is water—that even ordinary dis- 
tilled water may contain their germs ‘in such profusion that 
even so small a quantity as is introduced into a glass in rinsing 
is sufficient to render a relatively enormous volume of liquid 
fruitful.”—(Thirteenth Report of Medical Officer of Privy Council.) 
Dr. Sanderson recognises the particles of the germinal substance 
of bacteria as of such minuteness as to be not only invisible 
under the microscope, but insufficient to affect, so far as it was 
possible to ascertain, the optical purity of the water through 
which the electric beam was passed. We therefore do not 
recognise Dr. Bastian’s objections as fatal to the view that the 
lowest organisms observed ina putrefying infusion can be derived 
from pre-existing living particles. Such particles may exist un- 
detected, and may be transmitted by air, by water, or by both. 
The next argument, one that has always played a very im- 
portant part in the controversy, is that derived from the action of 
heat, which, it is urged, if of sufficient intensity, must destroy the 
life of any possibly pre-existent protoplasm in any given medium. 
Dr. Bastian has subjected organic infusions and saline solutions, 
in flasks from which air has been expelled, to temperatures 
varying from that of boiling water in the first series of experi- 
ments to upwards of 307° F.in other series. After the flasks 
had been put aside for certain periods the contents were mi- 
croscopically examined, with the result of the discovery, in many 
cases, of various fungoid organisms and ba¢teria particles. In 
considering thése results, we must at first not fail to make due 
allowance for the very difficult nature of the experiments, and 
