272 



OF THE PRIMARY TISSUES OF THE HUMAN BODY. 



The analyses of the long bones of the arm and leg correspond closely with 

 that of the femur ; but we observe that the proportions of ingredients in the 

 more spongy bones are widely different. It is difficult, however, to say how far 

 this variation is due to a difference in the proportions of gelatin and earthy 

 matter, in the actual osseous substance ; or how far it may be accounted for by 

 the presence of an increased proportion of membrane, forming the lining of the 

 cancelli. The same uncertainty must attend the explanation of the differences 

 that present themselves at different ages; as shown in the following table, 

 which gives a series of comparative analyses of the long bones, generally the 

 femur. 



Organic matter. 



Cartilage . ,' 



Fat ... 

 Inorganic matter. 



Phosphate of lime with ~\ 

 a little fluoride of cal- i- 

 cium . . *;<ij 



Carbonate of lime 



Phosphate of magnesia 



Soluble salts 



Foetus 

 6 months. 



40.38 

 a trace 



53.46 



3.06 

 2.10 

 1:00 



Foetus 

 7 months. 



34.18 

 0.63 



57.63 



5.86 

 1.10 

 0.60 



Child 

 2 months. 



33.86 

 0.82 



57.54 



6.02 

 1.03 

 0.73 



Child 

 5 years. 



31.28 

 0.92 



59.96 



5.91 

 1.24 



0.69 



Man 



25 years. 



29.70 

 1.33 



59.63 



7.33 

 1.32 

 0.69 



Woman 

 62 years. 



28.03 

 2.15 



63.17 



4.46 

 1.29 

 0.90 



100.00 100.00 100.00 100.00 100.00 100.00 



From this it will be seen, that there is a gradual diminution in the proportion 

 of animal matter, through life ; and a corresponding increase in the proportion 

 of the earthy components. But this is not nearly so great as is usually sup- 

 posed; and the greater solidity of the bones of old persons is doubtless owing 

 chiefly to the fact, that their cavities are progressively contracted, by the addi- 

 tion of new bony matter ( 265). 



263. The first Development of Bone may take place in the substance, either 

 of Membrane, or of Cartilage. 1 The tabular bones forming the roof of the 

 cranium afford a good example of the first, or intra-membranous form of Ossifi- 

 cation; for their place is but in part preoccupied by cartilage, only a membrane 

 being elsewhere interposed between the dura mater and the integuments (Fig. 

 64). This membrane is chiefly composed of fibrous fasciculi, corresponding with 

 those of the white fibrous tissues ; but amongst these are seen numerous cells, 

 some about the size of blood-disks, but others two or three times larger, contain- 

 ing granular matter ; and a soft amorphous or faintly-granular matter is also 

 found interposed amidst the fibres and cells. In certain parts, the fibres pre- 

 dominate; and in others, the cells. The process of ossification here seems at 

 first to consist in the consolidation of the fibres by earthy matter ; for the first 

 bony deposit consists of an irregular reticulation, very loose and open towards 

 its edges, where it frequently presents itself in the form of distinct spicula, which 

 are continuous with fasciculi of fibres in the surrounding membrane (Fig. 65). 

 The limits of the calcifying deposit may be traced by the opaque and granular 

 character of the parts affected by it; and it gradually extends itself, involving 

 more and more of the surrounding membrane, until the foundation is laid for 

 the entire bone. Everywhere, the part most recently formed consists of a very 

 open reticulation of fibro-calcareous spicula; whilst the older part is rendered 

 harder and more compact, by the increase in the number of these spicula, and 



1 In recent times, the development of Bone from Cartilage has received almost exclusive 

 attention; but the older opinion, that Bone is often developed in Membrane, has been 

 lately brought again into notice by Dr. Sharpey (Op. cit., vol. i. p. 83, et seq., Am. Ed.), 

 who has demonstrated its truth by Microscopic research. The statements in the text, 

 upon this part of the subject, are derived from Dr. Sharpey's observations, which the 

 Author has himself confirmed. 



