368 SPECIAL HISTOLOGY. 



still some points worth investigating in this way, particularly 

 with relation to the more recent statements of Brulle and 

 Hugueny, who, relying upon the circumstance, that, as they 

 assert, the decoloration of growing, coloured bones, is effected 

 merely by the absorption of the coloured portions, believe they 

 have found that the cylindrical bones also deposit osseous sub- 

 stance from within, particularly in the apophyses ; whilst on the 

 outer sui'face, absorption to the same extent takes place ; 

 statements upon which I will not, at present, give any decided 

 opinion, although at the same time I hold it as quite certain, 

 that in many places an absorption does take place, on the 

 exterior of the bone to a greater or less extent. It is only 

 by such an absorption that the enlargement of the foramen 

 magnum from the sixth year upwards, at which time the 

 portions of bone surrounding it are united, can be ex- 

 plained. And the same may be said with respect to the 

 arches of the vertebra, and numerous vascular and nerve- 

 openings (foramen ovale and rotundum of the sphenoid bone, 

 foramina inter transversaria, canalis caroticus, §c. §c). Con- 

 sequently, the law propounded by Serres (Meek. c Archiv/ 1822, 

 p. 455), that the openings in bone enlarge by the growth of the 

 individual pieces by which they are bounded, is wholly incorrect, 

 as applied to the openings and canals in the middle of bones ; 

 as had been already, to some extent, declared by E. H. Weber 

 and Henle ; and even in other cases it holds good only for 

 the earliest periods. 



The periosteal layers present a certain contrast to the osseous 

 tissue developed from cartilage. The former constitute prin- 

 cipally the firm cortex of the primarily cartilaginous bone, and 

 are characterised by the occurrence of Haversian canals and 

 their lamellar systems, whilst the latter produces the spongy 

 substance, and contains no vascular canals. It must not, how- 

 ever, be forgotten that even the periosteal layers all have, at 

 first, in a certain degree, a spongy structure, and in all these 

 bones, without exception, contribute, and frequently very essen- 

 tially, to the formation of the spongy substance ; moreover, 

 that in the cellular substance, which originates from the 

 cartilage, in the apophyses for instance, secondary layers, 

 similar to those of the Haversian canals, and of the spongy 

 substance which is formed out of the periosteal layers, only not 



