OF CARTILAGE. 31 



minimum of salts, and gradually more and more, until the whole 

 portion of cartilage obtains its due quantity ; or, the earthy 

 matter unites at first with some only of the smallest atoms of 

 the cartilage, combining, however, with these to the full propor- 

 tion which their capacity of saturation requires ; the remaining 

 atoms then gradually and successively receive their due portion 

 of the salts, so that each atom does not chemically combine with 

 them until it can become completely saturated. The latter 

 explanation, from the analogy with inorganic combinations, and 

 from the above-mentioned granulous appearance which cartilage 

 exhibits when undergoing ossification, appears to me by far the 

 more probable. For, according to the first view, the medullary ca- 

 naliculi, in the neighbourhood of which the deposition of earthy 

 matter first commences, ought to be surrounded, not by a gra- 

 nulous appearance, but by a dark shadow which should gradu- 

 ally fade away to a pale edge. 



I conceive the formation of the medullarv canaliculi in ossi- 

 fying cartilage to be similar to that of the capillary vessels, 

 which will be examined hereafter. We shall return to them 

 again, as also to the origin of the concentric laminas of bone. 



We will now briefly sum up the observations upon cartilage, 

 and refer to the phenomena of vegetable life, wdiich either accord 

 with or are dissimilar to them. Cartilage originates from cells, 

 every one of which has its special, and, in the first instance, 

 very thin wall ; precisely like those of vegetables. These cells 

 either lie closely together, and on that account are flattened 

 against one another, like those of plants (see pi. I, figs. 5 and 6), 

 or, there is intercellular substance present, and this again either 

 in so very small a quantity as to be visible only in situations 

 where three or four cells are in contact (see fig. 6, c), or in 

 so much greater quantity, as to prevent the contiguity of the 

 different cell-walls (pi. I, fig. 7 ; and pi. Ill, fig. 1.) Most 

 of the cells, at their earliest period of development (and per- 

 haps constantly) contain a nucleus, that is, a round or oval, and 

 sometimes hollow corpuscle (pi. I, fig. 5, a ; and pi. Ill, figs. 1 

 and 2), which again generally encloses one or two nucleoli. 

 The cartilage-cells originate in the first place by the formation 

 of the nucleus in the cvtoblastema, around which the cell is 

 afterwards formed, so that the latter at first closely encompasses 

 the nucleus. The nucleus advances slightly in growth after the 



