orm Peyer's patches, their precise office,
though seemingly like those of the lymphatic glands, cannot be positively
assigned, so far as I know, at the present time. It is of obvious
interest to learn it with reference to the pathology of typhoid fever.
It will be remarked that the coincidence of their changes in this disease
with enlargement of the spleen suggests the idea of a similarity of
function in these two organs.

The theories of the production of animal heat, from the times of Black,
Lavoisier, and Crawford to those of Liebig, are familiar to all who have
paid any attention to physiological studies. The simplicity of Liebig's
views, and the popular form in which they have been presented, have given
them wide currency, and incorporated them in the common belief and
language of our text-books. Direct oxidation or combustion of the carbon
and hydrogen contained in the food, or in the tissues themselves; the
division of alimentary substances into respiratory, or non-azotized, and
azotized,--these doctrines are familiar even to the classes in our
high-schools. But this simple statement is boldly questioned. Nothing
proves that oxygen combines (in the system) with hydrogen and carbon in
particular, rather than with sulphur and azote. Such is the
well-grounded statement of Robin and Verdeil. "It is very probable that
animal heat is entirely produced by the chemical actions which take place
in the organism, but the phenomenon is too complex to admit of our
calculating it according to the quality of oxygen consumed." These last
are the words of Regnault, as cited by Mr. Lewes, whose intelligent
discussion of this and many of the most interesting physiological
problems I strongly recommend to your attention.

This single illustration covers a wider ground than the special function
to which it belongs. We are learning that the chemistry of the body must
be studied, not simply by its ingesta and egesta, but that there is a
long intermediate series of changes which must be investigated in their
own light, under their own special conditions. The expression "sum of
vital unities" applies to the chemical actions, as well as to other
actions localized in special parts; and when the distinguished chemists
whom I have just cited entitle their work a treatise on the immediate
principles of the body, they only indicate the nature of that profound
and subtile analysis which must take the place of all hasty
generalizations founded