THE OSSEOUS SYSTEM. 369 



so much developed, appear to be formed. The morphological 

 and chemical relations of the matrix of these two forms of 

 osseous tissue have not as yet been determined. On the other 

 hand the bone-lacunse of both kinds of tissue do not present 

 the least difference.] 



§ 106. 



Bones not primarily cartilaginous occur, in Man, only in the 

 cranium. They originate outside the primordial cranium, be- 

 tween it and the muscular system, and thus within the struc- 

 tures constituting the vertebral system. They by no means 

 e"xist as membranous and cartilaginous capsules on the first 

 appearance of the cranium, their formation not commencing 

 till after that of the primordial cranium, from a secondary 

 blastema, whence, in contradistinction to the other primary 

 bones, the formative material of which exists prior to the com- 

 mencement of ossification, they are termed secondary bones — 

 or, also, because in most places they are in contact with 

 portions of the primordial cranium — covering or overlaying 

 bones (belegknochen). To this class belong, the upper half 

 of the expanded portion of the occipital bone, the parietal, and 

 frontal bones, the squamous portion and tympanic ring of 

 the temporal bone, the nasal, lachrymal, malar and palate 

 bones, the upper and lower jaw, the vomer, and apparently, 

 the internal lamella of the pterygoid process of the sphenoid, 

 and the cornua sphenoidalia. The blastema of these bones, 

 which differs from that of the primary bones, in its being 

 successively developed in a membranous matrix, simultaneously 

 with the process of ossification, not existing previously in any 

 considerable quantity, presents essentially, exactly the same 

 conditions as that of the periosteal layers, and is also ossified 

 in precisely the same way. 



[The notion that certain cranial bones, in man and the 

 Mammalia, are not developed from cartilage, is by no means 

 new, although the morphology of the question was first 

 established by Rathke, Keichert, Jacobson, and myself ; and 

 its histology by Sharpey and myself. But with respect 

 to the latter subject, a controversy still exists as to the 

 true nature of the ossific blastema (as also, of that ot the 



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