| Fuly 14, 1870] 
Pasteur, when we find him completely ignoring one of these 
points of view, interpreting all his experiments by the light of a 
foregone conclusion, and looking upon the different solutions 
employed solely as fluids which are destructive or not destruc- 
tive to hypothetical “ germs” at a given temperature. 
It should not be understood that I regard all acid solutions as 
having a low evolutional tendency. On the contrary, I believe I 
have helped to show in this paper that some acid solutions are most 
prone to undergo evolutional changes of a certain kind. These do 
not result in the production of Living things of a high type, but 
rather in an abundance of organisms of a comparatively low 
type. Itseems to me, however, after careful observation and 
experiment, that a neutral or slightly alkaline solution to which 
a few drops of acid have been added is always found, after 
agiven time, to contain a notably smaller number of organisms 
than an equal bulk of the unaltered solution. And conversely, 
having an acid solution whose productiveness is known, the 
number of organisms found in equal bulks under similar 
conditions, can almost always be notably increased in 
either one of them by the mere addition of a few drops 
of Jliguor fotasse, so as to render it neutral or slightly 
alkaline. This, as I previously pointed out, may be interpreted 
as an indication that alkalinity, or neutrality of the fluids, is 
more favourable than their acidity for the occurrence of evo- 
lutional changes. And thus the fact that organisms were never 
met with when an acid ‘‘eau de levire sucree”’ was used in re- 
peating the experiments of Schwann, though they were met with, 
on the contrary, in other experiments where portions of this same 
fluid had been used which had been rendered slightly alkaline 
by the addition of chalk, might be explained without the aid of that 
supposition which alone seems to have occurred to M. Pasteur. 
But, after reflection on this subject, it seemed to me quite 
within the range of probability, that the difference between acid 
and alkaline solutions in respect of the number of organisms 
which are to be found therein, when these have been simply ex- 
posed to ordinary atmospheric conditions, might be exaggerated 
after they had been exposed to the temperature at which water 
boils. \ It seemed quite possible that high temperatures might be 
more destructive to organic matter when this was contained in 
acid solutions than when it existed in alkaline solutions. Just 
as the acid seems to exercise a certain noxious influence even 
at ordinary temperatures, it may be conceived that this influence, 
whatever its nature, may be increased in intensity with the rise of 
temperature, and with the consequent greater facility for the dis- 
play of chemical affinities. Hot acids will frequently dissolve 
metals which would remain unaffected by them at ordinary tem- 
peratures ; and chemical affinities generally are notably exalted 
by an increased amount. of heat.. Just as the addition of 
an acid, therefore, to a previously neutral or slightly 
alkaline fluid containing organic matter in solution, appears 
to alter its character in some mysterious way, so may 
we assume that its action upon the unstable organic molecules 
goes on increasing in intensity as the fluid becomes hotter. So 
that, when two portions of a solution containing organic matter 
—the one neutral and the other acid—have been raised to a 
temperature of 100° C., whilst the organic matter of the one 
has been injured only by the mere action of heat ; that of the 
other solution, which has been acidified, has not only had to 
submit to the deleterious influence of the high temperature, 
but alsa to the increased activity of the acid at this temperature. 
Thus the ‘result would be that the amount of difference between 
the two solutions which existed before they had been heated, 
would be found more or less increased after they had been ex- 
posed to the high temperature, in direct proportion to the in- 
crease in intensity of the action of the acid produced by such 
high temperature. What we know concerning the precipitation 
of albumen in urine is quite in harmony with this view. When 
albumen is present, and the fluid has an alkaline reaction, mere 
boiling does not cause its precipitation, though, if the re- 
action had been acid,* the albumen present would have been 
precipitated, when, or even before, the fluid was raised te the 
boiling temperature. Or, the same result might have been 
brought about by the addition of a small quantity of acid to a 
portion of a neutral or alkaline albuminous specimen which had 
just been boiled without having brought about a precipitation of 
the albumen. Thus, the addition or presence of a small quan- 
tity of acid, in conjunction with an elevated temperature, 
is seen to be capable of producing results which cannot 
be pfoduced by the mere elevated temperature alone. But 
* Provided this was not due to the presence of a mere trace of nitric acid. 
NATURE 227 
the fact that an isomeric transformation of albumen can be 
brought about in this way—that albumen can be transformed so 
as to be no longer capable of remaining in solution—shows that 
a molecular change has been brought about by the influence of 
the acid working at high temperatures, which neither the acid 
nor the heat, working alone, are capable of effecting. 
With the view of throwing further light on this subject, on 
March 27 of the present year I made the following experi- 
ments :—A tolerably strong infusion of white turnip was pre- 
pared and subsequently filtered.* This had a decidedly acid 
reaction. It was then divided into two portions, one of which 
was allowed to remain unaltered, whilst to the other a few drops 
of Ziguor potasse were added, so as to give the fluid a very faintly 
alkaline reaction. This addition produced a slight alteration also 
in the naked eye appearance of the fluid ; the faintly whitish opal- 
esence which formerly existed disappeared, and was replaced by 
an equally faint brownish tinge. About an ounce of each of 
the two fluids was then placed separately in two small flasks. 
The fluids were not heated at all, but a piece of paper having 
been placed loosely in the neck of each so as to exclude dirt, 
they were exposed side by side to a temperature varying from 
75 to 85°F. After twenty-four hours,t+ the unaltered acid 
infusion merely showed a more decided opalesence approaching to 
cloudiness ; though that which had been rendered faintly alka- 
line, had a distinctly opaque whitish colour, and there was also a 
distinct pellicle covering more than one half of the surface 
of the fluid. In the three or four succeeding days the amount 
of opacity, of pellicle, and of deposit increased in both the 
fluids, though each of these continued to be more manifest 
in the alkaline than in the acid solution. After a week, however, 
the difference was scarcely appreciable, though on the whole, 
for about two weeks afterwards, the quantity of new matter 
seemed to be greater in the alkaline than in the acid solution. 
But, on the same morning that these two portions of the acid 
and alkaline infusions had been set aside for observation, I had 
placed with them vessels containing two other specimens of the 
same fluids. These had been previously treated in the following 
manner: The acid fluid and the alkaline fluid, after they had 
been placed in their respective flasks, and the necks of these had 
been drawn out, were then boiled for ten minutes, and at the 
expiration of this time—whilst ebullition was still continuing—. 
the drawn-out necks of the flasks were hermetically sealed in the 
blow-pipe flame. These vessels, therefore, were intended to 
show, by comparison with the other two, whether the difference 
produced by mere acidity or alkalinity of the solutions at low 
temperatures was or was not intensified by the action of heat. 
The flasks were all suspended in a group at the same time, and 
were, thenceforward, subjected to the same temperature. The 
results were as follows: After twenty-four hours the slightly 
alkaline fluid which had been boiled showed a slight though 
decided opalescence ; it was, in fact, very similar in appearance 
to the acid solution which had not been boiled. The boiled 
acid solution was, however, as clear as when the flask was first 
suspended, and so it remained, apparently quite unaltered, after it 
had been suspended a week, though the boiled alkaline solution 
had by this time become decidedly opaque, and also showed some 
flocculent matter lying at the bottom of the vessel. And now?, 
after they have been suspended more than three weeks, the acid 
solution still remains almost transparent, presenting only the 
faintest cloudiness, though with no pellicle or deposit at the 
bottom.§ The boiled alkaline fluid, however, presents a totally 
different appearance ; it is whitish and quite opaque, there is a 
very thick pellicle covering part of its surface, and also some 
whitish sediment at the botton of the flask. 
The difference which already exists between alkaline and acid 
solutions at ordinary temperatures is, then, seen to be most notably 
intensified after similar alkaline and acid solutions have been 
raised to a temperature of 100°C. And whilst these differences 
tend to substantiate the reality of the other mode of explanation 
(which I have suggested) of the discrepancies observed by 
M. Pasteur when he repeated Schwann’s experiments with acid 
and with alkaline organic infusions respectively, they may also 
* The turnip at this season of the year was however very poor and dry as 
compared with that which was employed in some of my earlier experi- 
ments (E-xferiments 4 to g) during the winter months. 
+ During the whole of this time the heat only varied between the limits 
mentioned. 
1 April 19, 1870. 
§ This solution was, therefore, much more backward in exhibiting signs 
of change than were the others which had been used in Experiments 4 to 8— 
a difference probably explicable by the poorer quality of the turnip used in 
this last experiment. ~ 
