CHAPTER  IX.
EXPERIMENTATION UPON ANIMALS.
bacteriology has to-clay become a science whose
principal objects are to discover the cause, explain the
symptoms, and prepare the cure of diseases. We can-
not hope to achieve these objects except by the intro-
duction of bacteria into animals, where their effects and
the effects of their products can be studied.
No one should more heartily condemn wanton cruelty
to animals than the physician and the naturalist. In-
deed, it is hard to imagine a class of men so much of
whose lives is spent in relieving pain, and who know so
much about pain, being* guilty'of the wholesale butchery
and torture accredited to them by a few of the laity,
whose eyes, but not whose brains, have looked over
the pages of physiological text-books.
Experimentation upon animals has given us almost
all our knowledge of physiology, most of our valuable
therapeutics, and the only scientific methods of treating
tetanus and diphtheria.
Experiments upon animals we must make, and, as
animals differ in their susceptibility to diseases, large
numbers and different kinds must be employed.
The bacteriological methods are not cruel. Two prin-
cipal modes of introducing bacteria are employed : the
subcutaneous injection and the intravenous injection.
Subcutaneous injections into animals are made exactly
as hypodermic injections are given to man.
Any hypodermic syringe that can be conveniently
cleaned and disinfected may be employed for the purpose.
Those expressly designed for bacteriological work and
most frequently employed are shown in Fig. 40." Those
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