lOI OSSEOUS SYSTEM. [sect. 1 05. 



whilst the latter produces the spongy substance and contains no vascular 

 canals. 



Still it is not to be forgotten, that all the periosteal layers are at first, to 

 a certain degree, of a spongy texture, and, in all these bones, invariably con- 

 tribute, and indeed frequently very essentially, to the formation of the 

 spongy substance ; further, that in the cellular substance also, which arises 

 from cartilage, in the apophyses for example, secondary deposits, similar to 

 those of the Haversian canals, and of the spongy substance derived from sub- 

 periosteal deposition, occur to great an extent. The chemical and morpho- 

 logical relations of the matrix of the two osseous tissues in question, are not 

 yet made out. On the other hand, the lacunse of both kinds present not the 

 slightest distinction ; but it must be kept in mind, that, as has been 

 shown in former sections, many of the bone-cells of the epiphyses, etc., seem 

 to be formed in secondary depositions, and do not originate from the 

 cartilage- cells themselves. 



§ 105. Bones not primarily cartilaginous were, in man, till 

 recently, only known to occur in the skull, but, according to 

 Bruch, the clavicle belongs to this division (compare the remarks 

 of H. Muller in Zeitsch.f. wiss. Zool. vol. ix.). The cranial bones 

 belonging to this section arise outside of the primordial cranium 

 between it and the muscular system, accordingly within the struc- 

 tures forming the vertebral system. When the skull first makes 

 its appearance as a membranous and cartilaginous capsule, they 

 are entirely absent, and only arise after the primordial cranium, 

 from a secondary blastema. From this circumstance, and to dis- 

 tinguish them from the primary bones whose formative material is 

 present at an earlier period, they are termed secondary bones, or 

 also, because they are in contact in most places, with parts of 

 the primordial skull, covering bones. The following parts beloug 

 to the secondary bones : the upper half of the flat portion of the 

 occipital bone, the parietal and frontal bones, the squamous por- 

 tion of the temporals and tympanic ring, the nasal, lacrymal, 

 malar and palate bones, the upper and lower maxillary, vomer, 

 and, as it appears, the inner lamella of the pterygoid process, and 

 the cornua sphenoidalia. The blastema of these bones, which, 

 different from that of the primary bones, is successively developed 

 into a membranous basis only when ossification takes place, and is 

 not previously present in large quantity, presents essentially the 

 same relations as that of the sub-periosteal depositions, and ossifies 

 exactly in the same manner. 



The opinion that certain cranial bones of man and mammalia are not deve- 

 loped from cartilage, is by no means new, still fiathke, lieichert, Jacdbson and I 

 were the first to establish the morphology of them ; and Sharpey and I the 



