STEUCTUEE. 81 



proportion of minute pores and lacuna;, wliicli contain soft matter scarcely 



separable in such experiments. 



Subjoined are the statements of two analyses. The one, by Berzelius, is well 



known ; the other, which nearly agrees with it, was performed by Middleton, in 



the laboratory of University College* 



Berzelius. Jliddleton. 

 Animal matter ........ 3.S"i50 — ?>'^■^^ 



Phosphate of lime ....... 5r04 — .oTll 



Carbonate of lime 11-30 — 10-31 



Fluoride of calcium ....... 2'00 — 1"90 



Magnesia, wholly or partially in the state of phosphate 1"10 — 1'67 

 Soda and chloride of sodium ..... 1'20 — 1'68 



In the compact substance of a femur that had been long buried. Aeby found 

 only lG-5 per cent, of animal matter. 



The phosphate of lime is peculiar, and passes in chemistry under the name of 

 the " bone-earth phosphate." It is a tribasic phosphate. Yon Bibra and A. 

 Milne-Edwards f found the proportion of the carbonate of lime to the jAot^phate 

 gi-eater in spongy than in compact tissue, and less in infantile bones generally 

 than in those of adults. The fluoiide of calcium is found in larger quantity in 

 fossil than in recent bones. 



Structure. — On sawing np a bone, it will be seen that it is in some 

 parts dense and close in texture, appearing like ivory ; in others open 

 and reticular: and anatomists accordingly distingnisli two forms of 

 osseous tissue, viz., the compact, and the spongy or cancellated. On 

 closer examination, however, especially with the aid of a magnifying 

 glass, it will be found that the bony matter is everywhere porous in a 

 greater or less degi'ee, and that the difference between the two varieties 

 of tissue depends on the different amount of solid matter compared 

 with the size and number of the open spaces in each; the cavities being 

 very small in the compact parts of the bone, with much dense matter 

 between them ; whilst in the cancellated texture the spaces are large, 

 and the intervening bony partitions thin and slender. There is, accord- 

 ingly, no abrupt limit between the two, — they pass into one another by 

 degrees, the cavities of the compact tissue widening out, and the reti- 

 culations of the cancellated becoming closer as they approach the parts 

 where the transition takes place. 



In all bones, the part next the surface consists of compact substance, 

 which forms an outer shell or crust, whilst the spongy texture is con- 

 tained within. In a long bone, the large round ends are made np of 

 spongy tissue, with only a thin coating of compact substance ; in the 

 hollow shaft, on the other hand, the spongy texture is scanty, and the 

 sides are chiefly formed of compact bone, which increases in thickness 

 from the extremities towards the middle, at which point the girth of 

 the bone is least, and the strain on it greatest. In tabular bones, such 

 as those of the skull, the compact tissue forms two plates, or tables, as' 

 they are called, inclosing between them the spongy texture, which in 

 such bones is usually named dijAoc. The short bones, like the ends of 

 the long, are spongy throughout, save at their surface, where there is a 

 thin crust of compact substance. In the complex or mixed bones, such as 

 the vertebrtB, the two substances have the same general relation to each 

 other; but the relative amount of each in diflTerent parts, as well as 

 their special arrangement in particular instances, is very various. 



* Philosophical Magazine, vol. xxv.,^p. 18. 

 t Ann. des Sc. Nat. 4me Serie, vol. xiii., 1860. 

 VOL. K. O 



