however, has been said to
send the reader interested in these questions to the original volumes
for further information. To one important practical point M. Pasteur,
in a letter to myself, directs attention:

*****

Permettez-moi de terminer ces quelques lignes que je dois dicter,
vaincu que je suis par la maladie, en vous faisant observer que vous
rendriez service aux Colonies de la Grande-Bretagne en repandant la
connaissance de ce livre, et des principes que j'etablis touchant la
maladie des vers a soie. Beaucoup de ces colonies pourraient cultiver
le murier avec succes, et, en jetant les yeux sur mon ouvrage, vous
vous convaincrez aisement qu'il est facile aujourd'hui, nonseulement
d'eloigner la maladie regnante, mais en outre de donner aux recoltes
de la soie une prosperite qu'elles n'ont jamais eue.

Origin and Propagation of Contagious Matter.

Prior to Pasteur, the most diverse and contradictory opinions were
entertained as to the contagious character of _pebrine_; some stoutly
affirmed it, others as stoutly denied it. But on one point all were
agreed. I They believed in the existence of a deleterious medium,
rendered epidemic by some occult and mysterious influence, to which
was attributed the cause of the disease.' Those acquainted with our
medical literature will not fail to observe an instructive analogy
here. We have on the one side accomplished writers ascribing epidemic
diseases to 'deleterious media' which arise spontaneously in crowded
hospitals and ill-smelling drains. According to them, the _contagia_ of
epidemic disease are formed _de novo_ in a putrescent atmosphere. On
the other side we have writers, clear, vigorous, with well-defined
ideas and methods of research, contending that the matter which
produces epidemic disease comes always from a parent stock. It
behaves as germinal matter, and they do not hesitate to regard it as
such. They no more believe in the spontaneous generation of such
diseases, than they do in the spontaneous generation of mice. Pasteur,
for example, found that _pebrine_ had been known for an indefinite time
as a disease among silkworms. The development of it which he combated
was merely the expansion of an already existing power--the bursting
into open conflagration of a previously smouldering fire. There is
nothing surprising in this. For though epidemic disease requires a
special _contagium_ to produce it, surrounding conditions must have a
potent influenc