out by the crackling of thorns under a pot of which Solomon speaks. So
far as I recollect, Solomon makes use of the image for purposes of
comparison; but I will not proceed further into that matter.

Two things must be obvious: in the first place, that every man who has
the interests of truth at heart must earnestly desire that every
well-founded and just criticism that can be made should be made; but
that, in the second place, it is essential to anybody's being able to
benefit by criticism, that the critic should know what he is talking
about, and be in a position to form a mental image of the facts
symbolised by the words he uses. If not, it is as obvious in the case
of a biological argument, as it is in that of a historical or
philological discussion, that such criticism is a mere waste of time on
the part of its author, and wholly undeserving of attention on the part
of those who are criticised. Take it then as an illustration of the
importance of biological study, that thereby alone are men able to form
something like a rational conception of what constitutes valuable
criticism of the teachings of biologists. [6]

Next, I may mention another bearing of biological knowledge--a more
practical one in the ordinary sense of the word. Consider the theory of
infectious disease. Surely that is of interest to all of us. Now the
theory of infectious disease is rapidly being elucidated by biological
study. It is possible to produce, from among the lower animals,
examples of devastating diseases which spread in the same manner as our
infectious disorders, and which are certainly and unmistakably caused
by living organisms. This fact renders it possible, at any rate, that
that doctrine of the causation of infectious disease which is known
under the name of "the germ theory" may be well-founded; and, if so, it
must needs lead to the most important practical measures in dealing