Thomas Gregor Brodie

“ In physical properties the white fibres are inextensible and extraordinarily strong, even being able, weight for weight, to carry a greater strain than steel wire. The yellow elastic fibres, on the other hand, are easily extensible and very elastic, but are far less strong than the white fibres. Their elasticity is exhibited by their straight course when viewed in a stretched preparation of areolar tissue, and this contrasts markedly with the wavy course of the bundles of white fibres seen in the same preparation. ”

“ They possess the power of dissolving both bone and cartilage matrix. Side by side with this solution process we may often see new formation taking place by the activity of the osteoblasts (fig. 10) . In this manner the whole framework of the bone may be gradually replaced. The process is most active in embryos and very young animals, but also continues during the whole life of an animal, thus effecting alterations in shape and structure of the whole bone. Growth in the length of a bone is effected by formation of new bone at either end of the shaft. ”

“ Each fibre generally runs parallel to the length of the muscle and if that muscle is short extends the whole length. Thus the one end of the fibre may be attached to tendon when the end is rounded off. The other end may also terminate in tendon or in the fibrous covering of bone in which case it is again rounded. In long muscles, however, the fibre may only extend a certain distance along the muscle, and it is then found to terminate in a tapering or bevelled end. ”

“ Abundant cartilage cells in a matrix containing many branching elastic fibres. Bone.—Bone is a connective tissue in which a considerable amount of mineral matter is deposited in the intercellular matrix whereby it acquires a dense and rigid consistency. If bone be incinerated so that the organic matter is burnt away, a residue of mineral matter is left. This consists chiefly of calcium phosphate, and amounts to as much as two-thirds of the weight of the original bone. ”

“ In most instances the cells are arranged with one another in a tissue to form bundles or sheets of contractile substance. In each bundle or sheet the cells are cemented to one another so that they may all act in unison. The cementing material is apparently of a membranous character and is so arranged that contiguous fibres are only separated by a single layer of membrane. ”

“ The cells lie separate and not in groups, and the amount of matrix between is commonly small. The white fibres may run in all directions or may chiefly run in one direction only. Under the microscope the tissue closely resembles a dense white fibrous tissue, only the cells enclosed in it are cartilage cells and not connective tissue cells. Owing to the presence of so much fibrous tissue this variety of cartilage is very much tougher than hyaline cartilage and less flexible. ”

“ The fibrillae are united to one another by interfibrillar substance to form bundles, of which there may be a considerable number in each muscle fibre. The bundles lie in a surrounding layer of sarcoplasm which apparently represents the remaining portion of unaltered protoplasm of the syncytium. This structure of muscle is best seen in the transverse sections of the fibres. A number of areas separated by a clear protoplasm are then to be seen. The areas are formed by the bundles of fibrillae seen in transverse section, the intermediate substance is the sarcoplasm. ”

“ Reticular Tissue.—This is a variety of connective tissue in which the reticulum of white fibres is built up of very fine strands leaving large interspaces in which the cells typical of the tissue are enclosed. The ground substance of the tissue is reduced to a minimum. Many connective tissue cells lie on the fibres which may in places be completely covered by them. This tissue therefore forms a groundwork holding together the main parts of an organ to form a compact whole. ”

“ The fat is either taken in as such by the cell, or, as is more commonly the case, manufactured by the cell from other chemical material (carbohydrate chiefly) and deposited within it in the form of small granules. ”

“ As these accumulate they run together to form larger granules and this process continuing, the cell at last becomes converted into a thin layer of living material surrounding a single large fat globule. The use of fatty tissue is to serve as a storehouse of food material for future use. ”

“ They possess alternate bands of light and dark substance which give them a striated appearance. When viewed under polarized light the dark substance is found to be doubly refracting or anisotropic, the light band is singly refracting or isotropic. ”