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MESSRS. J. TOMES AND C. DE MORGAN ON THE 
If we examine the fangs of temporary teeth when they are undergoing removal, 
similar states to those described as existing in the portion of femur will be found 
to obtain. A similar cellular mass will be seen to be closely applied to that surface 
of the tooth which is in process of removal, and the surface itself will present the 
characteristic emargination observed in the bone. When we connect these conditions 
with the fact that the nucleated cells which form the embryo have the power of 
appropriating the material which lies about them to the purpose of their own growth 
and their conversion into the various animal tissues, it is difficult to resist the belief 
that the cells which lie in contact with wasting bone and dentine, take up those 
tissues and use all or part of their element for the purposes of their own increase or 
multiplication, or else form a medium through which they are passed into the cir- 
culation. But as the process of absorption with concurrent development of cells is 
most active in primary bone where but few vessels exist, the former hypothesis seems 
the more probable. An objection may be raised to the supposition, that the bone is 
absorbed by the cells, on the ground of the density of the former; but it must be 
borne in mind, that as the density is gradually imparted to the bone through the 
agency of the adjoining soft parts, there seems no good reason for disbelieving that 
they may also be instrumental in its removal. 
Growth of 5owe.— Under this head will be described the extension of flat bones, 
the increase in the diameter of cylindrical bones, and the development of Haversian 
systems. 
If the advancing edge of a parietal bone be taken either from a human foetus or a 
foetal lamb, and the pericranium and dura mater be carefully removed from their 
respective surfaces, we shall find the growing bone still invested with soft tissue both 
on the outer and inner surface, which is prolonged from the free edge. When exa- 
mined under a favourable light this tissue will show differences of character in dif- 
ferent parts, varying with the distance from the bone at which the observations are 
made. Thus, if attention be directed to the part furthest removed from the bone, 
it will be seen that the membrane-like mass is composed of oval cells with slight 
prolongations from the extremities, which are frequently arranged in the form of bands 
of fibrous tissue (Plate VIII. fig. 26). Dr.SnARPEv has observed that the membrane into 
which the bone extends is like fibrous tissue in an early stage of development*, and 
this observation is strictly true when confined to the part indicated, but the analogy 
* Mr. Quain and Dr. Sharpey, oper. cit. cxlix. and page clix. Dr. Sharpky says, “ When further examined 
with a higher magnifying power, the tissue or membrane in which ossification is proceeding, appears to be made 
up of fibres and granular corpuscles, with a soft amorphous or faintly granular uniting matter. The fibres have 
the character of the white fibres, or rather fasciculi of the cellular or fibrous tissue, and are similaidy afi’ected by 
acetic acid. The corpuscles are for the most part true cells with an envelope and granular' contents ; some 
about the size of blood-particles, but many of them two or three times larger. In certain par'ts the fibres, but 
in most the corpuscles predominate, and on the whole the structure may be said to be not unlike that of fibrous 
tissue in an early stage of development.” KoLurKER, oper. cit. p. 289, confirms Dr. Sharpey’s statement, but 
denies that a fibrous arrangement can be traced in formed bone. 
