he,
as an introduction to his account of my theory, "are we not sometimes in
danger of forsaking old truths for new theories?"

Of my theory, he says: "The mere statement of it must satisfy our
readers that it is wholly untenable. It is well known that heat is
generated in every part of the system as well as the lungs. Whenever
oxygen and carbon unite, there it is developed; but it is imparted to
the _solids_ equally with the fluids; it maintains the temperature of
the whole body by radiations from the points where it is generated." ...
"It is believed that all those functions of the organism which are
necessary for the preservation of life, contribute directly or
indirectly to the production of animal heat; so that it is developed at
every point at which metamorphosis is occurring, and therefore not
merely in the lungs, but in the whole peripheral system."

The writer then observes, that "the heat of the venous blood as it
reaches the right side of the heart (according to Davy), varies only two
or three degrees from that of the aorta. Granting, then, that the blood
receives three degrees in the lungs, it is very evident that the
expansion produced by it would be too small to be appreciable. The
cause, then, is insufficient to produce the effects." The writer gives
me credit for having ingeniously supported my theory, and then politely
bows me out of the department of physiology into my more appropriate
sphere of educating girls.

In my reply, this sentence from Cuvier was chosen as a motto:
"Respiration is the function essential to the constitution of an animal
body; it is that which, in a manner, animalizes it; and we shall see
that animals exercise their peculiar functions more completely according
as they enjoy greater powers of respiration."[5] My reasoning was to
this effect: "It is in vain to say that cannot be, which is." When
two events are so conjoined in nature that one is the only invariable
antecedent of the other, then, according to all logic, we are bound to
conclude that the first is the physical cause of the second, even though
we cannot understand how it should be. Of the circulation, such living
respiration as produces heat is the invariable antecedent, and nothing
else is. The heart's action, as stated by our reviewer himself, is not
therefore respiration, and not the heart's action or anything else, is
the cause of the circulation. This argument is upheld by the fact that
circulation, varies not