The former part of this work has been devoted to researches upon
the systems common to the structure of all the apparatus, upon
the primitive systems, which form if we may so say the nutritive
parenchyma, the basis of all the organs, since there is hardly any one
of these organs in which the arteries, the veins, the exhalants, the
absorbents, the nerves and the cellular texture do not enter as a more
or less essential part. Each is at first a texture of these common
parts, then of other peculiar parts which particularly characterize
them.
The systems that will now be examined are not so generally extensive in
the animal economy. They belong only to some particular apparatus; thus
the osseous, the animal muscular, cartilaginous, and fibrous systems
are especially destined to the apparatus of locomotion; thus the
serous, mucous, and organic muscular systems enter especially into the
digestive, respiratory and circulatory apparatus; thus the glandular
system forms the apparatus of secretions, thus the cutaneous system
enters principally into the external, sensitive apparatus, &c.
All the systems that remain to be examined are then much more
insulated, perform a much less extensive part than those of which we
have been treating. Confined to certain apparatus, they are unknown
to the others, and have an independent life of their own, whereas the
primitive systems everywhere mingle their vitality with that of the
other organs, into whose composition they enter; most of them have
a kind of existence and external forms which distinguish them from
these last. The different parts which compose each, are almost always
insulated, not connected with each other; the bones, the muscles of
animal and organic life, the cartilages, the fibro-cartilages, the
medullary organs, the glands, the serous membranes, the hair, &c.
exhibit this insulation in a remarkable manner. Each portion belonging
to these different systems, has always between it and the other
portions of the same system many intermediate organs, which are of a
very different nature, and which consequently belong to other systems.
There are hardly any except the cutaneous, fibrous and mucous systems,
which are everywhere continuous in their different parts; yet this last
has no communication between that portion of it which is spread upon
the digestive and respiratory apparatus, and that which belongs to the
urinary and genital organs.
We have seen on the contrary that the primitive systems are everywhere
continuous, having no interruptions in them. The cellular, the
arterial, the venous, the absorbent, the nervous are so arranged, that
if it were possible to remove all the organs they enter, and leave them
alone, they would form a complete whole, formed differently according
to the different systems. The exhalants can also be considered as
everywhere connected, as we have seen. Suppose on the contrary that the
organs intermediate to the bones, the cartilages, the fibro-cartilages,
&c. should be removed, all the parts of these systems would
immediately be separated, and you would not have one continuous whole.
The order to be followed in the examination of these systems is of no
importance; we shall place them in the following order, which will
comprehend 1st, the osseous; 2d, medullary; 3d, cartilaginous; 4th,
fibrous; 5th, fibro-cartilaginous; 6th, animal muscular; 7th, organic
muscular; 8th, mucous; 9th, serous; 10th, glandular; 11th, cutaneous;
12th, epidermoid; 13th, and finally, the system of the hair.
Observe that nature is not confined to any methodical order, in
distributing these systems in the different apparatus; that she has
no regard to the great differences that she has established between
the functions. Each can at the same time belong to the apparatus of
functions that have no analogy. Thus the fibro-cartilaginous, which
is found especially in the organs of locomotion, and consequently in
animal life, enters also by the trachea into the respiratory apparatus;
thus the mucous system, everywhere destined to the organs of internal
life, belongs also to the external life in the conjunctiva, in the
nasal fossæ, &c. to generation in the vesiculæ seminales, in the
prostate, &c.; thus the glandular system pours by turns fluids upon the
organs of the two lives as upon those of generation; thus the serous
surfaces are spread upon parts whose functions have no resemblance
upon the brain and the stomach, for example, upon the articular
cartilages and the lungs, &c. Let us consider then the simple systems
abstractedly, if I may so say; let us describe them in an insulated
manner as materials distinct from each other, though united two by
two, three by three, four by four, &c. to form the partial edifices of
our apparatus, edifices from which results the general edifice of our
organs. Each of these apparatus is destined to exercise a determinate
function, and ought consequently to be classed as functions; it is in
this manner also that we shall distribute them in the Descriptive
Anatomy. But the simple systems, not tending to a common object, except
as they are united in the apparatus, we cannot, when considering them
separately, confine them to any classification borrowed from their
destination.