Page:Microscopicial researchers - Theodor Schwann - English Translation - 1947.pdf/153

Rh It had a gray and translucent appearance, exhibited no elasticity, and when examined with the microscope, presented no trace of its future structure. A gray cord, indistinctly marked with longitudinal fibres, was seen, in which a great many cell-nuclei might be recognized. I did not prosecute any further researches, as the presence of the nuclei was sufficient proof that there was nothing essentially different in the type of its formation.

On casting a retrospective glance over the class of fibre-cells which we have just been considering, we find that it forms a very natural and somewhat strictly defined group amongst the tissues. The tissues comprised in it are generated from nucleated cells, which are transformed into fasciculi of fibres by elongation, in the first place, and by the splitting of the bodies of the cells themselves into separate fibres at a subsequent period. The fundamental phenomenon previously described at page 39 is distinctly presented in the formation of these cells; a structureless, gelatiniform mass, the cytoblastema, is first present, and lies outside the cells already formed. The cells are developed in this, the nucleus being, in all probability, the earliest formation. The growth of the cells proceeds, and they become transformed into fibres in the manner described. The quantity of the cytoblastema continually diminishes in proportion to the cells or fibres which are forming, but probably part of it remains persistent between the fibres throughout the whole of life; in the mature condition, however, it exists in greater quantity in areolar than in fibrous or elastic tissue.

The mode of generation teaches us which parts of these tissues correspond to the constituents of those hitherto treated of. The elementary cells of areolar tissue, before undergoing change, correspond morphologically with the cartilage and epithelium-cells, the mucus-corpuscles, &c.; and as a fasciculus of fibres is generated from each cell of areolar tissue, a whole fasciculus of fibres of areolar tissue accordingly corresponds to what was an individual cartilage- or epithelium-cell, in the previous classes. The structureless cytoblastema between the fibres of areolar tissue corresponds, however, to the firm intercellular substance, forming the principal mass of most cartilages,