451 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. [December ?, 1870. 
at a higher temperature, and for that purpose he resorted 
to a very simple device. He had a long tube attached 
to the vessel in which his milk was boiling, bent over at 
the top, and brought down into a glass jar containing 
mercury to the depth of fifteen inches, or more. Of course, 
tinder these circumstances, the steam, which was being 
formed in the vessel, has to force its way up against the 
pressure of this mercury; the pressure of these fifteen 
inches of mercury was added to the pressure of air, and 
n total pressure was obtained, about half as much again 
as the pressure of the atmosphere amounted to. Of 
course, the milk had to boil at a higher temperature, 
corresponding to this higher pressure; and what did he 
find then? He proceeded, as before, with the experi¬ 
ment, closing the vessel while it was boiling, and not 
letting any air into it. He then kept it, and he found 
that no organisms appeared, even on keeping it a very 
long time; and he was, therefore, led to conclude that 
the milk must have contained in it some germs which 
could withstand the temperature at which the milk was 
boiling at first, but the vitality of which was destroyed 
by exposure to the higher temperature to which ho ex¬ 
posed it in the subsequent experiment. He had reason 
for that, for other experiments had been made by himself, 
.and by various other philosophers, which proved that 
many species of organisms can withstand a very high 
temperature without losing their vitality. In that 
respect, there are great differences amongst these little 
organisms which are remarkable and interesting, and 
wall, no doubt, be of value to future investigations. To 
give you an idea of the great variety presented by them 
in their power of withstanding heat, I may mention, that 
if I were to heat the contents of this carboy, in which the 
alcoholic fermentation is going on, to 60° Centigrade (100° 
being boiling-point Centigrade), which is rather more 
than half, the fermentation would be completely arrested, 
and the yeast-cells would be killed. On the other hand, 
the particles in milk are capable of withstanding 100°. 
Pasteur connected that fact with the circumstance that 
milk is alkaline, whilst this liquid is acid, and, as a rule, 
acid liquids destroy the vitality of these organisms at a 
lower temperature than alkaline liquids. That is not 
all. There are in the particles themselves great dif¬ 
ferences in their power of withstanding heat. Amongst 
the experiments which are particularly remarkable in 
that point of view, I ought to mention some with regard 
to the little spores of mould, and such-like things; for 
instance, the Penicillium glaucum, and some others. M. 
Pasteur collected some of these; and after taking a little 
piece of asbestos, or mineral flax, as it is sometimes called, 
and heating it in a flame, so as to destroy anything adher¬ 
ing to it, he put it carefully into a vessel in which some of 
this mould was growing, and moved it about, so that a 
number of particles of the seed of the mould might ad¬ 
here to it. He then heated the asbestos thus coated with 
dust to 120° C., a higher temperature than that to which 
the milk had been exposed; but after putting it into a 
liquid capable of feeding mould, he found that the mould 
made its appearance in considerable quantity, so that the 
germs of that particular organism were not destroyed 
by 120° of temperature. He even went higher, as far as 
125°, and found that that was not enough, but a little 
■over 125° killed them; 130° they cannot stand, so that, 
according to these observations, the limit appears to be 
between 125° and 130°. 
In all the cases of which I have been speaking, the 
ferments (because all these organisms are in their nature 
and functions analogous to the common ferments) were 
.removed from the substances which were employed be¬ 
fore the air and such-like materials carrying the germs, 
were brought in contact with them. 
AVith regard to processes for arresting fermentations 
and decomposition in liquids in which they are taking 
place, a number of observations have been made which 
are of considerable practical as well as theoretical im¬ 
portance, in relation to the results which I have been 
stating. Of course, mere heating, carried to a sufficient 
intensity, will arrest any process of fermentation or 
putrefaction which may be going on in a substance, and 
the applications of that process are, of course, exceed¬ 
ingly numerous and important. The only thing is, that 
we do not know, and it would be most hazardous to sup¬ 
pose that, in any particular case, we can name beforehand 
the temperature requisite to destroy a particular or¬ 
ganism. If any observer were to say that he has ex¬ 
posed a mixture to 100°, and, therefore, the organism 
must be destroyed, experience would refute him; if he 
said he had exposed it to 110°, or even 120°, expe¬ 
rience again would refute him; but if he) had exposed 
it to 150°, and asserted that he must have destroyed 
them, it is quite possible that experience might show 
that there are organisms which will resist even that tem¬ 
perature. It would have been almost impossible, some 
time ago, to admit, and we could not have admitted, that 
these organisms would have withstood the temperature 
which they have been found to withstand; and, there¬ 
fore, what temperature is sufficient to destroy the or¬ 
ganism in any case must be found by experiment, and 
that alone. Amongst other conditions for arresting the 
process of decomposition or putrefaction, which are in 
their nature like those of fermentation, I ought to men¬ 
tion the process of drying. All the processes of fermen¬ 
tation which I have been speaking of, and all others, 
which I could tell you of, are accompanied by moisture. 
Moisture is present, and is essential to them; in fact, 
these little organisms are exceedingly soft, wet things; 
moisture constitutes a great part of their substance, and 
in a dry medium they cannot live, or if the substance 
were dried, they would be destroyed by it. Applications, 
therefore, of a mere drying process arc amongst the most 
important and interesting of this class of agencies. Many 
of them are well known. For instance, the ordinary 
process of preserving fruit by means of drying it. Germs 
of putrefaction or decomposition may be present in the 
fruit; but if you merely take away the greater part of 
the moisture, you render the substance incapable of de¬ 
composing. Among the agents which serve for that 
purpose, there are some which abstract the water, not in 
a state of vapour, but in the liquid state; for instance, 
common salt. If you put a piece of fresh meat in contact 
with salt, or rub it over with the salt, the salt gradually 
absorbs the water, and draws the water out of the meat. 
The action is truly a drying action upon the meat, and 
it is effectual by a perfectly similar process to that which 
would go on if you exposed the meat in a dry chamber 
to a current of warm air. In like manner, of course, it 
is known to many persons that sugar is used just as salt 
is, to remove water from substances containing it in any 
quantity. If you were to rub any fruit or animal sub¬ 
stance with a sufficient quantity of dry sugar, you would 
get the sugar dissolved by the water which would be 
removed from the materials ; and amongst the observa¬ 
tions which are made in common life, there are some 
which bear, in an interesting and instructive way, upon 
what I have been saying to you. For instance, 1 have 
heard it said that ordinary jam—fruit and sugar, which 
have been boiled together for some time—keeps better if 
the pots into which it is poured are tied up whilst hot. 
The observation has been so frequently made that one 
was inclined to think that there must be some truth in 
it; and I think if we admit that the paper can act as a 
strainer in the same way as the cotton wool, you will, 
see at once that it must be as people suppose. Take two 
cases. Suppose one pot of jam, allowed to cool before it 
is tied down, little germs will fall upon it from the air, 
and they will retain their vitality because they fall 
upon a cool substance; they will be shut in by the paper 
and will soon fall to work decomposing the fruit. If 
you take another pot, perfectly similar, filled with a boil¬ 
ing hot mixture, immediately cover it over, though, of 
course some of the outside air must be shut in, any germs 
which are floating in it will be scalded, and in all pro- 
