NATURE 
159 
Even the cell itselfhas been changed. Until Schleiden’s 
time it was a little bleb filled with fluid ; we now regard it 
as a soft glutinous body constructed out of the albuminous 
protoplasm first distinguished by Mohl in 1845, and which 
is covered with a cellular integument, as the oyster is 
with its cell. After waxing eloquent over the cell as an 
entity, an “ego” by itself, and its relations to the outer 
world, Prof. Cohn says that science now teaches us that 
there is only one life and one cell, the cell of plants and 
of animals being essentially the same. The most highly- 
developed animal differs from the simplest plant only in 
the number and greater development of the matter com- 
posing the cells, but above all, to the more complete 
elaboration (Ardettsthetlung), and the stricter subordina- 
tion of the separate cells to the collective life of the or- 
ganism. Between the two extremes of the living world, 
the yeast-fungus and man, there is the same difference 
as there is between a group of individual men who do 
not know how to organise their strength, and a strictly 
-disciplined, well-ordered army suitably formed and well 
armed, and which, by the strict subordination of the 
many wills to the central authority, is always equal to 
the highest achievements. 
It is true that these scientific researches into biology 
have left as yet the most important questions unsolved. 
It is not yet possible to regard all life-processes as simple 
modifications of the other forces of nature and to ascer- 
tain their mechanical equivalents ; we cannot yet convert 
absolute heat or light into life; and although chemistry 
is daily doing more and more to bridge over the gaping 
chasm which once separated the organic and inorganic 
systems, it has not yet succeeded in finding out the pre- 
cise matter which exclusively supports the life-process, on 
which alone the cells subsist. Thus, then, the beginning 
of life is still wrapped in obscurity. 
After referring in this connection to the transmission 
of epidemics amongst plants, animals, and man, and to 
the microscopical labours of Leeuwenhoek, Ehrenberg, 
Gagniard-Latour, Schwann, and Kiitzing, Prof. Cohn 
_ * goes on to say that the investigators of the present time, 
to whom Pasteur has given a powerful impulse, have 
been the first to establish beyond doubt that without 
Bacteria no putrefaction, and without yeast-fungi no fer- 
mentation takes place ; that this decomposition is accom- 
plished only through the sustenance and living activity of 
those microscopic cells. 
Many a mystery of life will doubtless be unfolded to us 
if our epticians during the next twenty-five years should 
manage to raise the power of the microscope in the same 
proportion as in the previous quarter of a century, in which 
it has been at least quadrupled. The best microscope of 
Schiek and Plossl in 1846 did not magnify more than 500 
diameters ; the “immersion-lensxv.” of Hartnack over 2,000 
diameters. Still Dr. Cohn does not venture to hope that 
during the next twenty-five years all the questions of science 
which are at present being agitated will be solved. As 
one veil after another is lifted, we find ourselves behind a 
still thicker one, which conceals from our longing eyes 
the mysterious goddess of whom we are in search. 
Dr. Cohn, in concluding his eloquent address, attempts 
to point out the characteristics which distinguish the pre- 
sent from the past generation. In the former epoch 
students confined their researches to single and carefully 
marked off divisions of nature, without any regard to the 
neighbouring and closely allied regions, which must neces- 
sarily lead to the one-sided view that these divisions be- 
long to Nature herself. In the present generation, on the 
other hand, the several physical sciences have entered into 
the closest organic union. Physics and chemistry along 
with mathematical astronomy and geology, have been 
blended into a new science—the history of the develop- 
ment of worlds ; paleontology, systematic botany, and 
zoology have been joined into a united science of or- 
ganisms ; the physiology of plants and of animals have be- 
come coalesced in universal biology; the boundary 
between the organic and inorganic aspects of nature is 
being ever more and more obliterated, and out of the 
several natural sciences a single uniform, universal natural 
science is being constructed. 
But the deeper natural science penetrates from outward 
phenomena to universal laws, the more she lays aside her 
former fear to test the latest fundamental questions of 
being and becoming (Sez und Werden), of space and time 
of matter and force, of life and spirit, by the scale of the 
inductive method, and the more confidently she lifts her 
views concerning the universe out of the cloudy atmo- 
sphere of hypothesis into the clear ether of theory 
grounded on fact, so much the more will the gap be 
narrowed which since Kant has separated science from 
philosophy. Schiller’s advice to philosophers and men of 
science— 
‘*Feindschaft sei zwischen euch; noch ist das Biindniss zu friihe ; 
Nur wenn in Kampf ihr euch treant, dann wird die Wahr- 
heit enthiilt,”” 
has been followed for more than half a century, to the 
gain of the natural sciences, but often to the injury of 
philosophy, which would knock away the firm ground from 
under our feet. But since Herbart and Schopenhauer, and 
especially through Hartmann’s labours, have the two 
chief drifts of the work of the human mind been approach- 
ing; andif natural science has a mission to mould the 
future of our race, she must court the purifying influence 
of philosophical criticism: and this mission, in Dr. 
Cohn’s estimation, “the science of the future cannot 
reject. Its importance rests not merely in the much in- 
teresting and useful information which can be made 
available to trade and industry, for daily economy and 
universal civilisation ; she must build a sure foundation 
for our collective view of the universe, for our knowledge 
of ultimate and highest things. It must be no longer the 
case that even our most educated classes, in consequence 
of insufficient education, have neither interest nor in- 
telligence for the pursuit and acquisition of scientific 
knowledge. Moreover, science will be no more able to 
shun battle with other systems of the universe which have 
been hallowed by the traditions of a thousand years, 
than were Socrates and Aristotle, Copernicus and Gali- 
leo. Victory will lie on the side of truth. ; 
But if anxious souls should fear that with the advance 
of a scientific knowledge of the universe among the people, 
would come a breaking up of political and social order, 
let them be assured by the teaching of history, When 
we perceive the flash of an electric spark we certainly 
do not take at for a bolt darted by the revengeful 
Jupiter ; and as the vault of Heaven is resolved into air 
and light, so also must the Olympus be shattered which 
was built thereon. * But the ideas of the true, the beauti- 
