BY MOLECULAR COALESCENCE. 127 
described. The foramina in the osseous plates of this 
part replacing the lacune as found in other bones, and 
presenting a decided form of osseous areolar tissue. It is 
also still more corroborated by the areolated character of 
the osseous tissue, evident in a very early stage of develop- 
ment of the flat bones, as those of the cranium of feetal 
animals. In this case the recently ossified membrane has 
the appearance of being made up of meshes of various 
sizes produced by the interlacement of its fibres. The 
smallest meshes correspond to the lacunze of perfect bone, 
and appear to result from the plaiting or interlacing of 
the individual fibres; the largest ones corresponding to 
Haversian canals, are of very different sizes, and seem to 
be formed by a similar interlacing of fascicule of these 
fibres. This appearance is very distinct in the ossifying 
cranial bones of a very young pigeon; also in those of 
the human foetus at a very early period. The part where 
the ossifying process is just beginning to encroach upon 
the membrane, shows this fact most clearly. No prepara- 
tion is necessary beyond removing the integument, and 
putting the part into water or glycerine. The part of 
the process of ossification next to be considered relates 
to the chemical conditions under which the earthy matter 
is produced, and precipitated in a globular form. Now, 
as bone in most parts of the animal body is placed under 
the same anatomical conditions as the plates of shell, 
which, in the larger crustaceans, afford attachment to 
muscular fibres; and as the surface of the latter can be 
proved by proper tests to be moistened with a solution of 
an alkaline carbonate, and thus to be provided with one of 
the elements of which shell is formed ; and as it is shown 
that the other elements are brought into contact with the 
former through the medium of the circulating fluid where, 
