按键盘上方向键 ← 或 → 可快速上下翻页，按键盘上的 Enter 键可回到本书目录页，按键盘上方向键 ↑ 可回到本页顶部！
————未阅读完？加入书签已便下次继续阅读！
it。 When you find in some places that in an enormous thickness of
rocks there are but very scanty traces of life； or absolutely none at
all； and that in other parts of the world rocks of the very same
formation are crowded with the records of living forms； I think it is
impossible to place any reliance on the supposition； or to feel oneself
justified in supposing that these are the forms in which life first
commenced。 I have not time here to enter upon the technical grounds
upon which I am led to this conclusion；that could hardly be done
properly in half a dozen lectures on that part alone；I must content
myself with saying that I do not at all believe that these are the
oldest forms of life。
I turn to the experimental side to see what evidence we have there。 To
enable us to say that we know anything about the experimental
origination of organization and life； the investigator ought to be able
to take inorganic matters； such as carbonic acid； ammonia； water； and
salines； in any sort of inorganic combination； and be able to build
them up into Protein matter； and that that Protein matter ought to
begin to live in an organic form。 That； nobody has done as yet； and I
suspect it will be a long while before anybody does do it。 But the
thing is by no means so impossible as it looks； for the researches of
modern chemistry have shown usI won't say the road towards it； but；
if I may so say； they have shown the finger…post pointing to the road
that may lead to it。
It is not many years agoand you must recollect that Organic Chemistry
is a young science； not above a couple of generations old；you must
not expect too much of it； it is not many years ago since it was said
to be perfectly impossible to fabricate any organic compound； that is
to say； any non…mineral compound which is to be found in an organized
being。 It remained so for a very long period； but it is now a
considerable number of years since a distinguished foreign chemist
contrived to fabricate Urea； a substance of a very complex character；
which forms one of the waste products of animal structures。 And of
late years a number of other compounds； such as Butyric Acid； and
others； have been added to the list。 I need not tell you that
chemistry is an enormous distance from the goal I indicate； all I wish
to point out to you is； that it is by no means safe to say that that
goal may not be reached one day。 It may be that it is impossible for
us to produce the conditions requisite to the origination of life； but
we must speak modestly about the matter； and recollect that Science has
put her foot upon the bottom round of the ladder。 Truly he would be a
bold man who would venture to predict where she will be fifty years
hence。
There is another inquiry which bears indirectly upon this question； and
upon which I must say a few words。 You are all of you aware of the
phenomena of what is called spontaneous generation。 Our forefathers；
down to the seventeenth century； or thereabouts； all imagined； in
perfectly good faith； that certain vegetable and animal forms gave
birth； in the process of their decomposition； to insect life。 Thus； if
you put a piece of meat in the sun； and allowed it to putrefy； they
conceived that the grubs which soon began to appear were the result of
the action of a power of spontaneous generation which the meat
contained。 And they could give you receipts for making various animal
and vegetable preparations which would produce particular kinds of
animals。 A very distinguished Italian naturalist； named Redi； took up
the question； at a time when everybody believed in it； among others our
own great Harvey； the discoverer of the circulation of the blood。 You
will constantly find his name quoted； however； as an opponent of the
doctrine of spontaneous generation； but the fact is； and you will see it
if you will take the trouble to look into his works； Harvey believed it
as profoundly as any man of his time； but he happened to enunciate a
very curious propositionthat every living thing came from an 'egg'；
he did not mean to use the word in the sense in which we now employ it；
he only meant to say that every living thing originated in a little
rounded particle of organized substance； and it is from this
circumstance； probably； that the notion of Harvey having opposed the
doctrine originated。 Then came Redi； and he proceeded to upset the
doctrine in a very simple manner。 He merely covered the piece of meat
with some very fine gauze； and then he exposed it to the same
conditions。 The result of this was that no grubs or insects were
produced； he proved that the grubs originated from the insects who came
and deposited their eggs in the meat； and that they were hatched by the
heat of the sun。 By this kind of inquiry he thoroughly upset the
doctrine of spontaneous generation； for his time at least。
Then came the discovery and application of the microscope to scientific
inquiries； which showed to naturalists that besides the organisms which
they already knew as living beings and plants； there were an immense
number of minute things which could be obtained apparently almost at
will from decaying vegetable and animal forms。 Thus； if you took some
ordinary black pepper or some hay； and steeped it in water； you would
find in the course of a few days that the water had become impregnated
with an immense number of animalcules swimming about in all
directions。 From facts of this kind naturalists were led to revive the
theory of spontaneous generation。 They were headed here by an English
naturalist；Needham；and afterwards in France by the learned Buffon。
They said that these things were absolutely begotten in the water of
the decaying substances out of which the infusion was made。 It did not
matter whether you took animal or vegetable matter； you had only to
steep it in water and expose it； and you would soon have plenty of
animalcules。 They made an hypothesis about this which was a very fair
one。 They said； this matter of the animal world； or of the higher
plants； appears to be dead； but in reality it has a sort of dim life
about it； which； if it is placed under fair conditions； will cause it
to break up into the forms of these little animalcules； and they will
go through their lives in the same way as the animal or plant of which
they once formed a part。
The question now became very hotly debated。 Spallanzani； an Italian
naturalist； took up opposite views to those of Needham and Buffon； and
by means of certain experiments he showed that it was quite possible to
stop the process by boiling the water； and closing the vessel in which
it was contained。 〃Oh！〃 said his opponents； 〃but what do you know you
may be doing when you heat the air over the water in this way？ You may
be destroying some property of the air requisite for the spontaneous
generation of the animalcules。〃
However； Spallanzani's views were supposed to be upon the right side；
and those of the others fell into discredit； although the fact was that
Spallanzani had not made good his views。 Well； then； the subject
continued to be revived from time to time； and experiments were made by
several