xc BONE. 



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

 " bone-earth phosphate." It is a tribasic phosphate, consisting probably of 8 equiva- 

 lents of lime and 1 of water, with 3 eq. of phosphoric acid. Von Bibra and A. Milne- 

 Edwards * found the proportion of the carbonate of lime to the phosphate, greater in 

 spongy than in compact tissue, and less in infantile bones generally than in those of 

 adults. M.-Edwards considers that carbonate is formed from decomposition of the 

 basic phosphate by the carbonic acid of the blood, and that the proportion must 

 necessarily vary with the state of nutrition ; in infancy there is less decomposition 

 and also more rapid elimination of the products of decomposition, hence propor- 

 tionally less carbonate of lime. The fluoride of calcium is found in larger quantity 

 in fossil than in recent bones indeed, its presence in the latter was lately denied 

 altogether ; but since then, the original statements of Morichini and of Berzelius, 

 to the effect that it exists in recent as well as fossil bones, have been satisfactorily 

 confirmed. 



Structure. On sawing up a bone, it will be seen that it is in some parts 

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

 reticular : and anatomists accordingly distinguish two forms of osseous 

 tissue, viz., the compact, aud the spongy or cancellated. On closer ex- 

 amination, 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 degree, 

 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, accordingly, no abrupt limit between the two, they 

 pass into one another by degrees, the cavities of the compact tissue widening 

 out, and the reticulations of the cancellated becoming closer as they approach 

 the parts where the transition takes place. 



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

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

 within. In a long bone, the large round ends are made up 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 dip/oe. The short 

 bones, like the ends of the long, are spongy throughout, save at their sur- 

 face, where there is a thin crust of compact substance. In the complex or 

 mixed bone*, the two substances have the same general relation to each 

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

 special arrangement in particular instances, is very various. 



On close inspection, the cancellated texture is seen to be formed of slender 

 bars or spicula of bone and thin lamellae, which meet together and join 

 in a reticular manner, producing an open structure which has been com- 

 pared to lattice- work (cancelli), and hence the name usually applied to it. 

 In this way considerable strength is attained without undue weight, and it 

 may usually be observed that the strongest laminae run through the struc- 

 ture in those directions in which the bone has naturally to sustain the 

 greatest pressure. The open spaces or areolae of the bony network com- 



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



