The fibrous texture is extremely compact in the tendons; many appear
homogeneous at first view; but by examining them with care, we soon
distinguish fibres, connected by a small quantity of compact cellular
texture. Ebullition renders these fibres very evident; when we plunge
suddenly the tendon into boiling water at the place where it has
been cut transversely, they become a little thicker at this divided
extremity, swell as it were and are thus very evident. At the place
where they expand to form an aponeurosis or to unite to the periosteum,
these fibres can be distinctly seen without any preparation. On the
other hand, as we can always, as I have said, reduce artificially a
macerated tendon to an aponeurosis, and as in this state of maceration,
soft and loose, it yields to all the forms we wish to give it, it is
an excellent means of distinguishing the tendinous fibres. In this
experiment so easily repeated, I have never seen the spiral form of the
tendinous cylinders, of which some modern authors have spoken. These
fibres are in the tendon as at the place where they separate to form an
aponeurosis, that is to say in a right line.
Blood scarcely enters the vascular system of the tendons; but in some
inflammations, they are wholly penetrated by it. I have seen one of
those of the extensors, laid bare in a whitlow, so red, that it had
the appearance of a phlegmon. Yet I observed that this colour was not,
as in many other inflamed organs, dependant on the small red striæ,
an indication that the exhalants are filled with blood; but it was
uniform, as for example a body dyed red. In general, it appears that
of the whole fibrous system, it is the tendons which have the least
energetic degree of vitality, and the most obscure vital forces. By
dissecting them in a living animal I have found that they have exactly
the same arrangement as in the dead body; the white fluids that
penetrate them do not flow under the scalpel; they are dry and can be
removed by layers. They appear to have a very low temperature; for,
in general, the degree of heat of an organ is in proportion to the
quantity of blood vessels it receives.
If in the body they are at the general temperature, it is only because
the neighbouring organs communicate theirs to them. Caloric is not
disengaged in their texture.
The tendons have a remarkable affinity to gelatine and even the
phosphate of lime; where they slide upon a bone, and where they suffer
a great friction, they exhibit a hardness which authors attribute to
pressure, by comparing it to the callous hardening of the sole of the
feet, but which is owing evidently to an exhalation in the tendinous
texture of the two preceding substances, an exhalation which the motion
produces and from which arises a real ossification.
It is thus as we have said, that the different sesamoid bones are
formed, and the patella in particular, a bone the texture of which
evidently differs from that of the others, because in the midst of the
gelatine and of the phosphate of lime that penetrate it, there remains
in it a part of fibrous texture which is not seized upon by these
substances, and which is so considerable that its kind of vitality and
organization belong as much and more to that of the fibrous system,
than to that of the osseous.
Besides, if we detach the patella or any sesamoid bone, leaving with it
a tendinous portion of each side, and expose them to the action of an
acid, this calcareous substance is removed, the fibres of the bone are
exposed, and we see that they are a continuation of those of the tendon
which is then softened.
The muscles of organic life, and most of those which in animal life
form the sphincters, are destitute of tendons. This white texture,
those silver cords that are found in the heart, have not the nature of
the tendons of the limbs.