The fibrous organs have not been considered by anatomists in a general manner; no one has yet made a system of them. Separately described with the parts in which they are found, they cannot, in the present state of science, present us any of those great views, so useful to the practice of medicine, which show us each organic apparatus resulting from the combination of different systems, to which analogous ones are found in the other apparatus; so that though very different as it respects their functions, these apparatus are yet subject to the same diseases, because similar systems enter into their structure. I presented, two years since, various general views upon the fibrous membranes, which have opened the way; but these membranes are only a division of the fibrous system, which must be considered here more at length. ARTICLE FIRST. OF THE FORMS AND DIVISIONS OF THE FIBROUS SYSTEM. Though all the fibrous organs have precisely the same nature, and though the same fibre enters into the composition of all, yet the forms which they assume are extremely various; it is this variety of form, joined to that of their position and their functions, which has given them a different denomination, and made us designate them by the name of tendons, aponeuroses, ligaments, &c.; for there is no general denomination for the whole system, no word which answers for example to that of muscle, nerve, &c. which in the muscular, nervous systems, &c. gives an idea of the organization, whatever may be the form of the organ. I shall not create a word, I shall be easily understood without it. All the fibrous forms can be referred to two general ones; one of these is membranous, the other in fasciæ. The organ is broad and thin in the first; it is longer and thicker in the second. Thus the muscles, the nerves, the bones themselves exhibit alternately this arrangement in their conformation, as we see in the retina compared with the round nerves, in the muscular layers of the stomach and the intestines, compared with the muscles of locomotion, and in the bones of the cranium compared with those of the extremities. I. _Of the Fibrous Organs of a Membranous Form._ The fibrous organs arranged as membranes are, 1st, the fibrous membranes, properly so called; 2d, the fibrous capsules; 3d, the tendinous sheaths; 4th, the aponeuroses. 1st. The fibrous membranes comprehend the periosteum, the dura-mater, the sclerotica, the albuginea, the peculiar membranes of the kidney, the spleen, &c. &c. They are in general destined to form the covering of certain organs, into the structure of which they enter. 2d. The fibrous capsules, very distinct, as we shall see, from the synovial surfaces, are a kind of cylindrical sacs, which are found around certain articulations, especially those of the humerus and the femur, whose connexions with the scapula and the ilium they strengthen, by embracing with their two extremities, both surfaces of the articulation.