Page:Microscopicial researchers - Theodor Schwann - English Translation - 1947.pdf/55

Rh the case in the more completely ossified parts; there the cell-cavity remains behind, forming a dark indentation in the line, which as it advances renders the tissue transparent, and leaves the cavity a black spot, from which dark fibres, similar to those of the corpuscles of bone, issue in a stellated form. Shortly afterwards the fibres disappear, then the corpuscle gradually diminishes, and at last vanishes also, leaving a pale spot. Such an appearance could not be due to an air-bubble in the cell-cavity; for in that case, I think, the course of its exit might be followed. It is probably a more compact mass of earthy matter, which does not become dissolved so quickly as that contained in the substance of the cartilage. After this has become impregnated with earthy matter, the cell-cavities are also filled, and when so filled they are the osseous corpuscles. Similar observations might be instituted on the ossified cartilages of mammalia, in which the identity of osseous and cartilage-corpuscles was rendered more certain by Miescher’s researches. The next question which presents itself concerns the nature of those minute fibres which proceed in a stellated form from the osseous corpuscles. After the earthy matter has been withdrawn the corpuscles may still be seen, though rendered very pale by that process; the fibres, however, are not at all visible, although a formation corresponding to them is certainly present in the cartilaginous substance, and their extraordinary minuteness sufficiently explains the invisibility. The same formation might also exist before ossification, but be invisible from the like cause. As these fibres and the cell-cavities become filled with earthy matter simultaneously, and at a later period than the cartilaginous substance, and since they contain the earthy salts in a more compact and less easily soluble mass, it is probable that they are hollow tubes, that is, canaliculi which proceed from the cell-cavities, spreading out into the cartilaginous substance. According, therefore, to the view which we take respecting the cartilage-corpuscles, according as we consider them to be the cavities of cells, the walls of which have become thickened and blended, not only with one another but with the intercellular substance, so as to form the cartilaginous substance; or as we take them for the entire cells, and the intermediate substance of the cell-cavities as only intercellular substance, so must these tubes