174 CELLULAR TISSUE skill in these branches of art are a richly or- namented salt-cellar in the imperial gallery at Vienna, and a magnificent shield at Windsor castle. Of his larger works, the bronze group of Perseus, with the head of Medusa, in the piazza del Gran Duca at Florence, and his " Christ " in the chapel of the Pitti palace, are the finest. CELLUL1R TISSUE, a name given by the older anatomists to a tissue formed by a mix- ture of white and yellow fibres, extensively dif- fused in the animal body under the names of cellular, fibro-cellular, areolar, and fibrous tis- sue. The best name is areolar tissue, derived from the appearance of areolce, or meshes, left between the intricate crossings of the compo- nent fibres ; these were formerly mistaken for cells or cavities ; the old term cellular tissue, however, is so well and universally under- stood, that, though inaccurate, it will probably long be employed in this application. Its principal use seems to be to connect other tissues, allowing at the same time more or less freedom of motion between them ; it sup- ports the vessels and nerves in their minutest branches ; it is abundant under the skin and the mucous and serous membranes; it enters largely into the formation of membranes, hence often called cellular membranes, protecting the organs and cavities by their toughness and elasticity. The spaces of the cellular tissue are continuous throughout the body, as may be proved by artificial inflation by the blowpipe, and as is frequently seen in cases of emphysema and anasarca, where air or fluid is effused into its meshes. Under the microscope this tissue pre- sents two kinds of fibres, inextricably mingled in various proportions. The one is white and inelastic, disposed to a waved or zigzag arrange- ment in bands of unequal thickness, creased longitudinally by numerous streaks ; the lar- gest of these bands are often -5^-5 of an inch wide ; the component fibres do not branch, ac- cording to Hassall; this is the white fibrous tissue. The other kind of fibre is elastic, of a yellowish color, composed of branched fila- ments disposed to curl when not put on the stretch ; they are generally about -^jVy of an inch thick, interlacing with the others without becoming continuous with them ; this is the yellow fibrous tissue. These two elements of the cellular tissue may be at once distinguished by submitting it to the action of dilute acetic acid, which instantly causes the former to swell up and become transparent and soft, while it causes no change in the latter. Cellular tissue is especially abundant in parts which enjoy free motion, as in the face about the eyes and cheeks, the anterior part of the neck, the arm- Eit, the flexures of the joints, the palm of the and, and the sole of the foot ; the superficial and most movable muscles are separated by thicker layers than the deep-seated ones, and the constituent fibres are held together by it during contraction; almost every part of the vascular system is held in place by this tissue, wjiose elasticity protects the vessels during the necessary movements of the body ; even its own minute but numerous vessels are conducted and enveloped by this all-pervading tissue. It is difficult to say where cellular tissue is not found, unless it be in the teeth, in bone, in cartilage, and in the cerebral substance, where its presence would be manifestly useless. The internal vital organs most exposed to external violence are protected by large quantities of this substance, as the pancreas, kidneys, colon, and genito-urinary apparatus ; every organ has its investing covering of cellular tissue, and its processes of the same penetrating and holding together its component parts. It is especially abundant just under the skin, to facilitate its movements, and it exists in uncommon quan- tity about and in the interior of the mammary glands. Thus this tissue seems to serve as a bond of union between parts, as an element of strength and protection rather than as a sub- stance of primary importance in itself; wher- ever elasticity is required, the yellow fibrous tissue is most abundant, while the white fibrous tissue prevails in parts demanding resistance and tenacity ; and the openness of the meshes is in proportion to the amount of mobility need- ed. The amount of cellular tissue varies with age and temperament, being greatest in youth and least in old age ; the plumpness and round- ness of the arms in children and females de- pend to a great extent on the presence of this substance around the joints, which in man are prominent and angular. Like other soft solids, it contains a small quantity of serous fluid in its interstices, which is favorable for the free movement of the fibres ; an unnatural increase of this fluid in the subcutaneous cellular tissue causes the form of dropsy called oedema, so common about the feet and ankles, and indi- cated by the skin pitting under the pressure of the finger. In the English training process it is rapidly lessened, with a remarkable diminution of the bulk of the body ; its natural and slow disappearance is seen in old age and in chronic disease, in which the skin, especially about the face and neck, becomes wrinkled and flabby. Its power of reproduction is great, and it is rapidly formed both in healthy and morbid growths ; it undergoes the putrefactive process slowly, and when boiled yields gelatine from its white fibrous element. So extensive a tis- sue as this must of necessity become involved in many diseases ; it is subject to all the effects of inflammation, with suppuration and mor- tification; to the infiltration of blood, serum, air, and urine ; to induration, tumors, and un- natural increase and degeneration. In com- mon inflammation of this tissue, the capillaries become congested, and a part of their contents escapes, more or less tinged with blood; the coagulable lymph thus effused causes the hard- ness of circumscribed inflammation ; this may be removed by absorption, or may become softened by the deposition of purulent matter, constituting an abscess, whose walls are formed
