there canals, and
consequently different organs; to cause these canals and these
organs to vary there by reason of the diversity both of the
movements as well as the nature of the fluids which occur there;
finally to enlarge, to elongate, to divide and to gradually
strengthen (_affermir_) these canals and their organs by the matters
which are formed in the fluids in motion, which incessantly separate
themselves, and a part of which is assimilated and united with
organs while the rest is rejected.'

"Secondly, the continual employment of an organ, especially if it is
strongly exercised, strengthens this organ, develops it, increases
its dimensions, enlarges and extends its faculties.

"This second law of effects of exercise of life has been understood
for a long time by those observers who have paid attention to the
phenomena of organization.

"Indeed, we know that all the time that an organ, or a system of
organs, is rigorously exercised throughout a long time, not only its
power, and the parts which form it, grow and strengthen themselves,
but there are proofs that this organ, or system of organs, at that
time attracts to itself the principal active forces of the life of
the individual, because it becomes the cause which, under these
conditions, makes the functions of other organs to be diminished in
power.

"Thus not only every organ or every part of the body, whether of man
or of animals, being for a long period and more vigorously exercised
than the others, has acquired a power and facility of action that
the same organ could not have had before, and that it has never had
in individuals which have exercised less, but also we consequently
remark that the excessive employment of this organ diminishes the
functions of the others and proportionately enfeebles them.

"The man who habitually and vigorously exercises the organ of his
intelligence develops and acquires a great facility of attention, of
aptitude for thought, etc., but he has a feeble stomach and strongly
limited muscular powers. He, on the contrary, who thinks little does
not easily, and then only momentarily fixes his attention, while
habitually giving much exercise to his muscular organs, has much
vigor, possesses an excellent digestion, and is not given to the
abstemiousness of the savant and man of letters.

"Moreover, when one exercises long and vigorously an organ or sys