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 organic combinations, and 
from the above-mentioned granulous appearance which cartilage 
exhibits when undergoing ossification, appears to me by far the 
moreprobable. 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 medullary 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 laminz of bone. 
We will now briefly sum up the observations upon cartilage, 
and refer to the phenomena of vegetable life, which 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 pl. 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 (pl. I, fig. 7; and pl. ITI, 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 (pl. I, fig.5, @; and pl. ILI, 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 cytoblastema, 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 
