412 
NATURE 
[Sep¢. 22, 1870 
open for us to suppose that such minutest visible living things 
lad proceeded from the growth of pre-existing germs which 
were themselves invisible, 
This being, as I conceive, the real state of the case, and Pro- 
fessor Huxley being in the position of a person, admitting* that 
a crystal can be produced de wove, admitting also the fossibilily 
that a living thing may so arise, but denying that there is any 
evidence worthy of serious consideration to show that a living 
thing can at the present time originate de move, let us see on 
what evidence he has come to this conclusion, and what other 
evidence he has practically ignored. 
In the first place, he does not attempt to deny—he does not 
even allude to the fact—that Living things may and do arise as 
minutest visible specks, in solutions in which, buta few hours be- 
Sore, no such specks were to be seen, And this is in itself a very 
remarkable omission. Vhe statement must be true or false, 
aid if true, as Laud others affism, the question, which Professor 
Ifuxley has sct himself to discuss, is no longer one of such a 
simple nature as he repre-ents it to be. It is henceforth settled, 
so far as visid/e germs are concerned, that living things caz come 
into being withcut them. It can now, at ail events, be said 
that some Living things do not come from z7s/d/e germs. Who, 
therefore, in the face of this fact will say that the doctrine omne 
vivum ex vivo remains unshaken? Perhaps, however, this par- 
ticular case where an exception to the rule is possible, was not 
known to Professor Huxley. I wish I could bring mysclf to 
believe that this was really the case. Certain it is that had he 
recognised the existence of this apparent exception to the general 
rule he would then have had to discuss a much more diffi- 
cult question, and he would have been compelled szriously 
to inquire into the value of experiments whose existence he 
has now almost ignored. Again then I affirm that multitudes 
of minute living things may and do gradually appear in fluids, 
beneath the microscope, where no v¢.7b/e germs previously ex- 
isted. Here the hypothesi> that every living thing procceds 
from a pre-existing living thing may break down, and those 
who wish to establish the continuity of this rule are bound to 
discuss the nature of the existing evidence which is in fevour 
of the notion of the living things in question originat.ng from pre- 
existing zwvisid/e germs, as against the opposite fossidz/ity of their 
having originated de xvvo. The buiden of proof resis as much 
on the one side as it rests on the other. We cannot safely con- 
tinue to affirm a rule until the cases in which it seems doubtful 
have been thoroughly discussed. Analogy is often but a 
treacherous guide. 
And, when we come to the discussion of this hypothesis as to 
the origin of living things from germs which are invisible, all 
alike are rendered, to a certain extent, helpless. No one, then, 
can come forward, as Redi is said to have done, ‘*strong with 
the sense of demonstrabie fact,” and any one who wishes or 
calls upon his opponent to demonstrate the truth of his views, 
when the question is one concerning the presence or absence of 
inzvisibie germs, shows himself to be ignorant as to how the 
matter in dispute can a.one be settled. The subject is one in 
which direct demonstration must give place to reasouing, although 
experiment and observatiun may and must be brought forward 
in support of this. Let those, however, who wish to proclaim 
the universality of the rule ome vivum ex vivo, recollect that, if 
they expect to influence reasonable peuple who are themselves 
cumpetent to form an opinion on the subject, they are bound 
to consider the fossii/e exception to which their attention is 
directed, and to weigh the evidence for and against the origin 
of these minutest visible living specks from germs which ave 
supposed tu exisi, but which are zzzszdle. 
The reason, indeed, which seems to induce most people to 
believe that living things cannot arise de xvvo, is because in 999 
cases out of a thousand which come under their actual notice, 
there cannot be a question that a living thing originates from a 
pre-existing living thing. A rule, which is of such apparently 
universal application, they say, is most likely to be the rule which 
applies to any doubtful case. Much is made out of this argu- 
mient, which is, of course, a very valid one so far as it goes. But, 
on the other hand, knowing, as I have pointed out, that any living 
things which arise, de novo, from non-living matter, must appear 
in solutions as minutest v.sible specks, it need not be a matter of 
much surprise that this mode of generation is one which is un- 
familiar to the world at large. Llave we not seen, indeed, that 
the most accomplished bioiogist, provided with the very best 
* I suppose this may fairly enough be presumed even in the absence of 
any specific statement as to his belief on the subject. ‘his is, however, 
an assuimpiion on my part. 
microscope hitherto made, though he gets down to a minimum 
visible stage of less than z57+5y5" In diameter is just as powerless 
in face of the hypothesis of zxvisible germs as those who 
worked with the rude microscopes which alone were in vogue 
two centuries ago? And, more especially is this consideration 
one which presses for earnest attention, when we further con- 
sider that some of the mirute living things which first appear as 
tiniest specks in homogeneous solutions grow into Sacteria, 
and that concerning the real origin of these, i such cases, we 
are as ignorant as we were concerning the real origin of crystals, 
when they appeared in previously homogeneous solutions. The 
probavility that these latter have originated de novo has, of late 
year., had to be established by a process of reasoning similar to 
what we are obliged to have recourse to, if we wish to throw 
light on the question of the origin of these specks of Living 
matter. Bacteria grow, and after a time aggregations of them 
may be converted under our very eyes in.o /wngus-spores * 
capable of throwing out a filaments and of developing into 
perfect plants. Nobody pretends to know, however, how, or 
whether, the Zacterca which make their appearance in a homo- 
geneous solution have originated from invisible /wngus-emana- 
uons ; all that we know is, that in suitable solutions, appearing 
homogeneous to high microscopic powers, in the course of a 
very short time, a multitude of perfectly motionless specks 
appear, in situations where previously no specks had existed. 
Being motionless and diffused their number cannot be accounted 
for by any supposed rapidity of multiplication—the only possible 
explanations seem to be, either that the specks have originated 
from as many pre-existing germs which were invisible, or else 
that they have proceeded from material collucations, which haye 
been initiated in the fluid itself by virtue of the molecular pro- 
perties of the substances in solu.ion, and the physical forces or 
sum total of ‘* conditions,” acting thereupon. 
And this is really the question which has to beconsidered. When 
it is supposed that Living things do appear independently of pre- 
existing living matter, in certain solutions nothing more than 
this is supposed to have taken place. New Living matter is 
presumed to have appeared—independently of germs—in the 
solutions within these flasks, and to have made 7/s appearance 
as living matter may, in certain other fluids, under our very eyes, 
in the form of minutest visible specks, which have been exposed 
to great and long-continued heat in hermetically sealed masses. 
And similar.y such specks, are the only forms of Living matter 
which are supposed to be capable of arising de novo. Once 
formed, it is true, one of these living specks may develop 
into a Bacterium, and this may develop into a Vibrio or a 
Leptothrix filament, whilst another of the living specks may de- 
velope at once into a /ungus-spore.t It should be clearly 
understood, however, that a// the Living taings which are siup- 
posed to arise out of non-living matrials, are presumed to appear 
in fluids, and gradually to emerge from the region of the iuvisible 
ints that of the visible; at which latter point they, for us, con- 
stitute specks less than z5y'y50” in diameter. 
Making no statements whatever upon this subject, however, 
in support of the dvctrine which he considers to remain un- 
shaken, let us see what line of argument Professor Huxley has 
taken, in order to establish the validity of this belief to the 
members of the British Assuciation for the Advancement of | 
Scence, ; , 
The ‘‘long chain of evidence” which he considers sufficient 
to allow us still to place faith in the rule omne vivum ex vivo, 
seems to me, to be, in reality, utterly inadequate for this pur- 
pose, ad incapable of aliecting the real question at issue. 
Nothing that has been said bears at all upon the problem as to 
whether it is possible that the minute living specks to which J] 
have referred do or do not originate de xove, though, as I have 
already said, it is these, and such as these only, which are pre. 
sumed to originate after this fashion. If he had really wished to 
influence those who are conversant with the subject, it would have 
been absolutely imperative for Prof. Huxley to have entered fully 
into the consideration of a subject which I will presently mention, 
but to which he makes only the most casual allusion. All the 
facts which he has trought forward—all the references to the 
investigations of Spallanzani, Schultze and Schwann, Cagni- 
ard de la Tour, Helmholtz, Schroeeder and Deutsch, Tyndall 
and Pasteur—are simply contributions to the ‘* Atmospheric 
Germ Theory,” tending to show that there are germs of living 
things in the air, and tat the living things found in some solu- 
ions may have been deveioped therefrom. But although differing 
* See Narurg, No. 35, p. 173, Fig. 3. 
t See NaturE, No, 37, pp. 221, 223. 
