and destruction of the fluids of the animal body, set up by minute
organisms which are the cause of this destruction and of this
disturbance; and only recently the study of the phenomena which
accompany vaccination has thrown an immense light in this direction,
tending to show by experiments of the same general character as that to
which I referred as performed by Helmholz, that there is a most
astonishing analogy between the contagion of that healing disease and
the contagion of destructive diseases. For it has been made out quite
clearly, by investigations carried on in France and in this country,
that the only part of the vaccine matter which is contagious, which is
capable of carrying on its influence in the organism of the child who is
vaccinated, is the solid particles and not the fluid. By experiments
of the most ingenious kind, the solid parts have been separated from
the fluid parts, and it has then been discovered that you may vaccinate
a child as much as you like with the fluid parts, but no effect takes
place, though an excessively small portion of the solid particles, the
most minute that can be separated, is amply sufficient to give rise to
all the phenomena of the cow pock, by a process which we can compare to
nothing but the transmission of fermentation from one vessel into
another, by the transport to the one of the torula particles which
exist in the other. And it has been shown to be true of some of the
most destructive diseases which infect animals, such diseases as the
sheep pox, such diseases as that most terrible and destructive disorder
of horses, glanders, that in these, also, the active power is the
living solid particle, and that the inert part is the fluid. However,
do not suppose that I am pushing the analogy too far. I do not mean to
say that the active, solid parts in these diseased matters are of the
same nature as living yeast plants; but, so far as it goes, there is a
most surprising analogy between the two; and the value of the analogy
is this, that by following it out we may some time or other come to