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MESSRS. J. TOMES AND C. DE MORGAN ON THE 
on the surface of the bone osteal cells are developed and gradually take its place ; a 
few cells become developed into lacunal cells ; the earthy salts are added, and con- 
currently lacunae and canaliculi are formed ; we then have bone presenting the usual 
characters of that tissue*. In bone developed in the foregoing manner, we find the 
canaliculi not merely extending to the surface of the cell-wall, or anastomosing with 
the canaliculi of lacunal cells lying in contact with it, but extending freely in all direc- 
tions and passing through or amongst the ossified cells, and establishing rich plexuses 
of anastomosis. Indeed we see the boundary of the original lacunal cells only in those 
cases where the lacunse have but few, or are entirely devoid of canaliculi. It would 
appear to be a law, to which there are few if any exceptions, that when anastomosis 
is established between adjoining lacunse, the lacunal cells blend with the contiguous 
parts, and are no longer recognisable as distinct bodies. The process by which the 
cylindrical bones are increased in diameter is in all essential points similar to that 
described as pertaining to the growth of flat bones. Similar osteal and lacunal cells 
are present, but the relative amount of the matrix is greater ; moreover the osteal 
cells have a disposition to assume a linear arrangement corresponding to the direction 
of the laminse of the contiguous bone. In these lines the cells are placed so close to 
each other as to leave but little room for intervening tissue, but between the lines an 
appreciable amount may be recognized (Plate IX. fig. 31). This appearance however 
varies in different specimens. In one the cells predominate, in another the transparent 
tissue is the more abundant. Generally the younger the animal the greater will be the 
amount of the intervening transparent tissue, and the smaller the number of the osteal 
cells. But in all cases, whatever the age of the subject, or from whatever part of the 
skeleton the specimen be taken, the cells and the intermediate tissue become blended 
in the process of ossification, and the whole presents a uniform granular appearance, 
excepting in the instances in which lamination is strongly developed, or in those 
which have been noticed in the previous part of the paper. We frequently find portions 
of bone where the osteal cells, lacunal cells, and intermediate tissue aie so perfectly 
fused together that neither can be recognized, but in their place we have a minutely 
granular mass, divisible only into lacunm and canaliculi and the tissue in which they 
lie imbedded. In Plate IX. fig. 32, taken from the tibia of a foetal lamb, the osteal 
and lacunal cells have become blended to a considerable extent, but without the 
* When speaking of the growth of cartilage, it was stated that the bulk of that tissue at the epiphysis 
increased laterally by the division of the cells, but the fact that it also increased on the free surface of the 
greatly enlarged cartilaginous epiphysis of the fcetus by a process similar to that by which the diameter of 
bones is increased, was reserved to be described in connection with the latter subject. If a longitudinal section 
be taken from the epiphysis of a foetal long bone, including some portion of the perichondrium, it vstII be seen that 
the cartilage passes gradually into a more or less fibrous tissue, which forms the exterior of the part. Amongst 
the fibres will be found numerous elongated cells, which on tracing the specimen inwards will be seen to be 
similar to the cartilage cells at and near the surface of the tissue, while the fibres will be seen to give way to 
or become converted into hyaline tissue, as shown in Plate IX. fig. 30, in which the cartilage is indicated 
at a, and the cells included in the fibrous tissue at b. 
