perience and discovery. We shall probably never
fill all the gaps; but this will not prevent a profound belief in the
truth of the theory from taking root in the general mind. Much less
will it justify a total denial of the theory. The man of science who
assumes in such a case the position of a denier is sure to be stranded
and isolated. The proper attitude, in my opinion, is to give to the
theory during the phases of its growth as nearly as possible a
proportionate assent; and, if it be a theory which influences
practice, our wisdom is to follow its probable suggestions where more
than probability is for the moment unattainable. I write thus with
the theory of _contagium vivum_, more especially in my mind, and must
regret the attitude of denial assumed by Professor Virchow towards
that theory. 'I must beg my friend Klebs to pardon me,' he says, 'if,
notwithstanding the late advances made by the doctrine of infectious
fungi, I still persist in my reserve so far as to admit only the
fungus which is really proved while I deny all other fungi so long as
they are not actually brought before me.' Professor Virchow, that is
to say, will continue to deny the Germ Theory, however great the
probabilities on its side, however numerous be the cases of which it
renders a just account, until it has ceased to be a theory at all, and
has become a congeries of sensible facts. Had he said, 'As long as a
single fungus of disease remains to be discovered, it is your bounden
duty to search for it,' I should cordially agree with him. But by his
unreserved denial he quenches the light of probability which ought to
guide the practice of the medical man. Both here and in relation to
the theory of evolution excess upon one side has begotten excess upon
the other.

====================

NOTE.--As might have been expected, Professor Virchow, shows himself
in practice far too sound a philosopher to be restricted by the canon
laid down in his critique of Dr. Haeckel. In his recent discourse
upon the plague, he asks and answers the question, 'What is the
_contagium_?' in the following words: 'Et qu'est-ce que le _contagium_? A
mon avis, l'analogie de la peste aver le charbon contagieux me parait
si grande qu'il me semble possible de trouver un organisme
microscopique qui contient le germe de l'affection. Mais jusqu' a
present on a peu cherche a trouver cet organisme.'--Revue
Scientifique, March, 1879.

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