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.