RECENT MICROSCOPY. 
15 
group of facts than by actual observation. Mr. Crace Calvert, 
in a paper read in May before the Eoyal Society, alludes to 
the great difficulties of such investigations, and he specially 
signalises those arising from the rapid development of minute 
life under certain conditions. White of egg, for example, 
mixed with water free from life, and exposed for a quarter of 
an hour to the air in August or September, exhibited life in 
abundance. Even a momentary exposure to the atmosphere 
seems sufficient, as long since pointed out by Pasteur; but 
no one has hitherto been able to detect in the atmosphere 
that abundance of divers germs which the followers of Pouchet 
consider must exist therein if the panspermist theory is true. 
Few would now deny that living forms and their germs may 
exist in a condition so small, or so transparent, as to elude our 
best instruments ; and it becomes practically impossible to start 
with establishing the negative proposition, that no life or germ 
exists in the materials or the vessels experimented with. One 
of the most interesting of Mr. Crace Calvert’s researches 
related to the amount of heat minute germs of life will bear. 
He allowed life to be developed in sugar solutions contained 
in small stout tubes, and then gradually brought them in an 
oil bath to various temperatures. At 212° most of the living 
objects had disappeared, but some small black vibrions and 
three common ones still moved energetically. At 300°, sus- 
tained for half an hour, two ordinary and one or two black 
vibrions still moved; but at 400° and 500° no life was 
visible. The tubes were examined twenty-four days after the 
heating. 
Much mental confusion exists on these matters from a vague 
use of the terms 66 life ” and 44 living.” If we consider the 
complicated phenomena exhibited by creatures enjoying the 
higher forms of life, and if calling them 44 alive ” is a short 
way of summing up their properties and actions, and if the 
same word 44 alive ” is used to sum up the smaller range of pro- 
perties and actions of the most rudimentary objects of which 
life of any sort can be predicated, it is obvious that no precise 
meaning is attached to the term. Notwithstanding Dr. Lionel 
Beale’s experiments, we have no reason for assuming that there 
is an abrupt and sharp transition from non-living to living 
matter, or that life consists in the action of a 44 principle ” upon 
inorganic substances. We do not know what life is, and the 
less pretension of knowledge that does not exist the better the 
prospects of science will become. 
Various questions of development are intimately connected 
with that of the origin of life, and many of them are much 
easier to study; and the more they are worked out the nearer 
we may approximate to some logical generalization that may 
conduct us beyond the regions open to direct research. 
