ration of
poisonous compounds within the body. This conclusion, which comes to
us with a presumption almost amounting to demonstration, is clinched
by the fact that virulently infective diseases have been discovered
with which living organisms are as closely and as indissolubly
associated as the growth of Torula is with the fermentation of beer.

And here, if you will permit me, I would utter a word of warning to
well-meaning people. We have now reached a phase of this question
when it is of the very last importance that light should once for all
be thrown upon the manner in which contagious and infectious diseases
take root and spread. To this end the action of various ferments upon
the organs and tissues of the living body must be studied; the habitat
of each special organism concerned in the production of each specific
disease must be determined, and the mode by which its germs are spread
abroad as sources of further infection. It is only by such rigidly
accurate enquiries that we can obtain final and complete mastery over
these destroyers. Hence, while abhorring cruelty of all kinds, while
shrinking sympathetically from all animal suffering--suffering which
my own pursuits never call upon me to inflict,--an unbiassed survey of
the field of research now opening out before the physiologist causes
me to conclude, that no greater calamity could befall the human race
than the stoppage of experimental enquiry in this direction. A lady
whose philanthropy has rendered her illustrious said to me some time
ago, that science was becoming immoral; that the researches of the
past, unlike those of the present, were carried on without cruelty. I
replied to her that the science of Kepler and Newton, to which she
referred, dealt with the laws and phenomena of inorganic nature; but
that one great advance made by modern science was in the direction of
biology, or the science of life; and that in this new direction
scientific enquiry, though at the outset pursued at the cost of some
temporary suffering, would in the end prove a thousand times more
beneficent than it had ever hitherto been. I said this because I saw
that the very researches which the lady deprecated were leading us to
such a knowledge of epidemic diseases as will enable us finally to
sweep these scourges of the human race from the face of the earth.

This is a point of such capital importance that I should like to bring
it home to your intelligence by a single