In the midst of the mucous state of the embryo, we cannot distinguish
the fibrous organs. All is confounded; it is not until many other
organs are formed, that we discover any traces of them. Those in the
form of membranes appear at first like transparent nets; those arranged
in fasciæ seem to be a homogeneous body. In general the fibres are not
distinct in the first age; the aponeuroses, the fibrous membranes,
the tendons, &c. do not exhibit any trace of them; all then seems
to be uniform in the texture of the fibrous organs. In the fœtus of
seven months, we begin to distinguish the white fibres. Few at first,
and distant from each other, they gradually approximate after birth,
are arranged in a parallel manner, or cross in different directions,
according to the organ which they finally possess themselves of
entirely at a certain age. It is especially on the phrenic centre of
the diaphragm, the dura-mater, the aponeurosis of the thigh, that we
easily make these observations.
As the fibres are developed in the fibrous organs, they have more
resistance and hardness. In the fœtus and in the first years, they are
extremely soft and easily yield. Their whiteness has a tinge wholly
different from that of a more advanced age; they are of a pearly white.
It is only gradually that they arrive at that degree of force that
especially characterizes them.
It is to this softness, this want of resistance of the fibrous system
in the first years, that the following phenomena must be attributed.
1st. The articulations yield at this age to motions which the stiffness
of the ligaments afterwards renders impossible; all extensions can
then be carried beyond their natural degree. We know that it is at
this period that tumblers begin to practice; they would never be able
to execute those extraordinary motions, which astonish us, if habit
did not preserve in them from infancy the power of these motions. 2d.
Luxations are in general rare in the first age, because the fibrous
capsules yield and do not break. 3d. Sprains have then less serious
consequences. 4th. The inflammatory swellings under the aponeuroses are
rarely susceptible of those strangulations oftentimes so severe at the
adult age. 5th. This softness of the fibrous system accommodates itself
also in the tendons, the ligaments, the aponeuroses, &c. on the one
hand to the multiplicity and frequency, and on the other to the want of
power of the motions of the infant.
I would remark, that although the fibrous system has in the first age a
softness of texture nearly uniform in all the parts that belong to the
same order, yet it is more or less developed according to the regions
in which it is found. In general, when it belongs to the organs that
are early developed, as to the brain by the dura-mater, to the eyes
by the sclerotica, &c. it has in proportion more size and thickness;
but it is only in its dimensions, and not in its intimate organization,
that these differences then exist.
It is probable that this mode of organization of the fibrous system
has an influence, at the period of which we are treating, upon its
degree of vitality and consequently upon its diseases. We know that
rheumatism, which appears very probably to affect this system, is
rarely the attendant of children of the first age; that in a hundred
patients affected with it, there are ninety at least above the age of
fifteen or sixteen years.
Subjected to ebullition, the fibrous system of the fœtus and the infant
easily melts, but does not take that yellow colour, which it constantly
has, when boiled in the adult age; we know that the jellies made from
young animals are much whiter than those from older ones.