Sroney—Lnergy Required for the Life of Bacilli. 155 
It is further evident that if this be the source of energy upon 
which bacilli and cocci have to draw, the minutenes of their 
narrowest dimension will be of advantage—probably essential— 
to them. Presumably it would only be limited by such other 
necessary conditions as may forbid the diminution of size being 
carried beyond a certain point. The diameter of a bacillus is 
frequently as small as half or a third of a micron, which brings 
it tolerably well into the neighbourhood of some molecular 
magnitudes. 
The transference of energy here suggested may be what occurs 
notwithstanding that it does not comply with the Second Law 
of Thermodynamics, which states that heat will not pass from a 
cooler to a warmer body, unless some adequate compensating 
event occurs, or has occurred, in connexion with the transference. 
This law represents what happens when vast numbers of mole- 
cular. events (which are the real events of nature) admit of being 
treated statistically, and furnish an average result. It, therefore, 
has its limits: and the communication of energy from air to 
minute organisms, which is described above, is an example of a 
process which is exempt from its operation; since this trans- 
ference is supposed to be brought about by a discriminating 
treatment of the molecules that impinge upon the bacillus of 
precisely the same kind as that which Maxwell pictured as nade 
by his well-known demons. It, therefore, belongs to the recognized 
exception’ to the Second Law of Thermodynamics, viz. that which 
1 Addition received February 20, 1893.]—I# the reader has any doubt as to whether 
the process described in the text is one of those that contradict the Second Law of 
Thermodynamics, he may satisfy himself on this head by the following considerations :— 
Imagine a perfect heat-engine within an adiabatic envelope, with some bacilli and 
an abundance of their mineral food, all being at one temperature. If events take 
place as supposed in the text, the bacilli receive sufficient energy from the surrounding 
medium to enable them to assimilate their mineral food, and thereby to grow and 
multiply. Meanwhile the medium becomes cooler. We may then suppose that the 
new bacilli which have come into existence, and all the excreta, are used as fuel in the 
heat-engine, and that its refrigerator is as near as we please to being at the tem- 
perature to which the medium has been reduced. ‘The combustion of the fuel may take 
the form of resolving the bacilli and excreta back into the mineral substances from which 
they had been evolved, except that these are now at the temperature of the combustion. 
Let us next reduce this temperature in the heat-engine to the temperature of the re- 
frigerator. During this process a portion of the heat may be converted into mechanical 
energy, and at the end of the process everything within the enclosure is in the same 
state as at the beginning, with the sole exceptions that some of the bodies within the 
