Page:Cellular pathology as based upon physiological and pathological histology.djvu/39

Rh fore, we have a structure which entirely corresponds with a vegetable cell.

It has, however, been customary with authors, when describing cartilage, to call the whole of the structure of which I have just given you a sketch (fig. 2, a—d) a cartilage -corpuscle, and in consequence of this having been viewed as analogous to the cells in other parts of animals, difficulties have arisen by which the knowledge of the true state of the case has been exceedingly obscured. A cartilage-corpuscle, namely, is not, as a whole, a cell, but the external layer, the capsule, is the product of a later development (secretion, excretion). In young cartilage it is very thin, whilst the cell also is generally smaller. If we trace the development still farther back, we find in cartilage, also, nothing but simple 'cells, identical in structure with those which are seen in other animal tissues, and not yet possessing that external secreted layer.

You see from this, gentlemen, that the comparison between animal and vegetable cells, which we certainly cannot avoid making, is in general inadmissible, because in most animal tissues no formed elements are found which can be considered as the full equivalents of vegetable cells in the old signification of the word; and because in particular, the cellulose membrane of vegetable cells does not correspond to the membrane of animal ones, and between this, as containing nitrogen, and the former, as destitute of it, no typical distinction is presented. On the contrary, in both cases we meet with a

Fig. 2. Cartilage-cells as they occur at the margin of ossification in growing cartilage, quite analogous to vegetable cells (cf. the explanation. to fig.. 1). a — c. In a more advanced stage of development, d. Younger form.