OF CARTILAGE
the cartilage is about to become, but is not as yet, ossified), and placed under the compressorium, the cells will be seen to lie so closely in it, that the space occupied by them may be estimated at three fourths, and that of the intercellular substance at one fourth of the whole volume. Many of the cells which have become separated by the process of cutting, float already in the fluid; and on slightly compressing the preparation many more become loose, and flow out in streams from the intercellular substance into the surrounding fluid. The intercellular substance is too soft to prevent the separation, but at a subsequent period of development this cannot be effected. According to Meckauer the cartilage-corpuscles may also be isolated by boiling. I once succeeded in crushing one of these young carti- lage-cells while still in connexion with the preparation. The first effect of the compressorium was to produce an extension of breadth; it then suddenly shrank together, whilst a clear fluid streamed out, thus proving the contents of the cell to be fluid and transparent. Now, inasmuch as these cells present in different instances a more or less granulous appearance, it follows that the cells of ossifying cartilage must have a peculiar investing membrane, which is granulous, and thus that they are actual elementary cells, in our sense of the word, and neither mere excavations in the substance, nor perfectly solid corpuscles. The appearance of the cells which float about entirely accords also with this view, for while their contents seem to be clear, the cells look granulated. All of them contain a very beautiful oval or circular, not flattened cell-nucleus, situate upon the internal surface of the wall, and this nucleus encloses one or two very distinct nucleoli; in short, they in every respect accord with the elementary cells of most of the other tissues. By the aid of acetic acid we may also frequently succeed in rendering the cell-walls visible upon a thin lamella of cartilage, and as the cell-contents are at the same time disolved by the acid, it has the additional advantage of bringing the nucleus into view, which is sometimes indistinct in consequence of the granulous nature of the contents. Plate III, fig. 2, exhibits a portion of cartilage so treated with acetic acid; it is taken from the as yet unossified portion of the ilium of an embryo pig of five inches in length. The cell-walls, with their double outlines, may be seen, and both the illuminated and
