170 OSSEOUS SYSTEM. [sect. 90. 



distinctly seen when they are connected with these, running 

 parallel to them, and penetrating from without and from within 

 into the substance of the diaphyses, so as to be interposed between 

 the other lamellae in masses of o'oi'" to criz'" in diameter. In 

 the interior of the compact substance, the Haversian systems of 

 canals in man are usually so close together, that the existence of 

 special collections of lamella? between them is out of the question ; 

 and lamellae, which in cross sections apparently run parallel to the 

 surface in the situation referred to, will be found almost always 

 to belong to canals running horizontally, for it is but rarely 

 that more distinct intermediate masses also appear here, though 

 this is generally the case in mammalia; moreover, certain inter- 

 stitial lamellae may be regarded, with Tomes and De Morgan, as 

 the remains of Haversian systems partly absorbed. The individual 

 lamellae, of the above-described systems have the same thickness 

 as those of the Haversian canals, and their number varies from 10 

 to 100. 



Hitherto, we have spoken only of the diaphyses of long bones. 

 In the apophyses of the long bones the thin cortex, as was to be 

 expected, exhibits but few Haversian systems of lamellae, although 

 these present the same characters as in other parts. The outer 

 fundamental lamellae are scanty ; within, they are wholly wanting, 

 on account of the spongy substance here present. In this, the 

 very scanty Haversian canals present the usual systems of lamellae, 

 but thin, and the remaining substancej according to the nature of 

 the osseous network, consists of a lamellated and fibrous tissue, 

 which, in general, has the same course as the contours of the 

 medullary spaces and cells. The fiat and short bones present, in 

 their interior, the same arrangement, whilst their cortex deviates 

 from that of the long bones only in this, that the fundamental 

 lamellae in the flat bones run parallel to both the surfaces of these 

 bones. The thickness of the fundamental lamellae in the cranial 

 bones (parietal bone) is sometimes the same within and without, 

 viz., 008"' to o*i6'"; sometimes they are wholly absent externally 

 in parts where the bone is very vascular, and the Haversian lamellae 

 extend almost to the surface. 



With respect to the intimate structure of the osseous lamellae, 

 a sufficiently thin section of dry bone, polished, and especially a 

 transverse one, usually presents, apart from the lacunae and canali- 

 culi, an extremely fine but very distinct punctuation in the lamellae, 

 which are generally not very distinct, so that the whole osseous 

 tissue appears granulated, and as if composed of closely arranged 



