BAUR, ON OSSIFICATION OF CARTILAGE. 29 
trast with the wholly colourless cartilaginous matrix sur- 
rounding it, and which has regained its transparency owing 
to the solution of the calcareous particles, a clear proof that, 
in this case, the two tissues are not in a Condition of con- 
tmuous transition, but simply in juxtaposition. Further on, 
the separate, occasionally thickened and laminated osseous 
rings are seen to become more and more closely approxi- 
mated, until, the mtervening layer of cartilage having en- 
tirely disappeared, they come into immediate contact. Thence 
it follows that the matrix of the primordial cartilage takes no 
part in the formation of the bone-substance, but that, on 
the contrary, notwithstanding the calcification, it undergoes 
absorption. This result, derived from observ ation, has been 
long rendered probable by the chemical ElnGene of these 
tissues, seeing that the diversity in chemical constitution 
between bone-cartilage and the hyaline cartilage-substance 
was opposed to the notion that the latter remained im a per- 
sistent form in bone. In explanation, therefore, of the pro- 
cess of ossification, we must assume either a chemical change 
or a molecular replacement of the one substance by the other. 
But from what has been stated, it is proved that this replace- 
ment is not one of a merely chemical, molecular nature, but 
histological. The organic basis of bone is no more anatomi- 
eally than it is chemically identical with the matrix of hya- 
line cartilage. The latter is incapable of true ossification ; 
its calcification’ is a process accompanying ossification, it is 
true, but one of an essentially different nature. 
The osseous substance which makes its appearance in car- 
tilage is a new formation in the cartilage-cavities, but it does 
not commence at once as such, its formation being preceded 
by that of a blastema, consisting of simple cells, and a soft 
intercellular substance. Now this blastema corresponds in 
every respect with the ossifying layer of the periosteum, and, 
like that, with immature connective tissue, and it should, 
therefore, be described as of the nature of connective tissue. 
Its ossification takes place by the calcification of the persis- 
tently homogeneous intercellular substance, and the transfor-’ 
mation of its cells mto bone-corpuscles. 
Thus, in cartilage also, ossification is preceded by a forma- 
tion of connective tissue—in this case effected through the 
cartilage-cells. Connective tissue is thus the only foundation 
of the formation of bone. We thus have a histogenetic 
demonstration of the chemical correspondence of the so- 
termed bone-cartilage with the collagenous tissues, and, in 
general, established the hitherto overlooked unity in the 
genesis of the osseous tissue, inasmuch as the formation of 
