e is
becoming settled in favor of the lactic. But the whole solvent agency of
the digestive fluid enters into the category of that exceptional mode of
action already familiar to us in chemistry as catalysis. It is therefore
doubly difficult of explanation; first, as being, like all reactions, a
fact not to be accounted for except by the imaginative appeal to
"affinity," and secondly, as being one of those peculiar reactions
provoked by an element which stands outside and looks on without
compromising itself.

The doctrine of Mulder, so widely diffused in popular and scientific
belief, of the existence of a common base of all albuminous substances,
the so-called protein, has not stood the test of rigorous analysis. The
division of food into azotized and non-azotized is no doubt important,
but the attempt to show that the first only is plastic or nutritive,
while the second is simply calorifacient, or heat-producing, fails
entirely in the face of the facts revealed by the study of man in
different climates, and of numerous experiments in the feeding of
animals. I must return to this subject in connection with the
respiratory function.

The sugar-making faculty of the liver is another "catalytic" mystery, as
great as the rest of them, and no greater. Liver-tissue brings sugar out
of the blood, or out of its own substance;--why?

Quia est in eo
Virtus saccharitiva.

Just what becomes of the sugar beyond the fact of its disappearance
before it can get into the general circulation and sweeten our tempers,
it is hard to say.

The pancreatic fluid makes an emulsion of the fat contained in our food,
but just how the fatty particles get into the villi we must leave Brucke
and Kolliker to settle if they can.

No one has shown satisfactorily the process by which the blood-corpuscles
are formed out of the lymph-corpuscles, nor what becomes of them. These
two questions are like those famous household puzzles,--Where do the
flies come from? and, Where do the pins go to?

There is a series of organs in the body which has long puzzled
physiologists,--organs of glandular aspect, but having no ducts,--the
spleen, the thyroid and thymus bodies, and the suprarenal capsules. We
call them vascular glands, and we believe that they elaborate colored and
uncolored blood-cells; but just what changes they effect, and just how
they effect them, it has proved a very difficult matter to determine. So
of the noted glandules which f