BY MOLECULAR COALESCENCE. 1a va 
illustrated catalogue of the histological series contained in 
the Museum of the Royal College of Surgeons, Plate XVI, 
fig. 14, there is a representation of perfect rhombohedral 
masses resembling crystals, taken from the shell of the 
common oyster. Such crystals are found, when treated with 
muriatic acid, to leave a residue of the same form as the 
original crystals, from which circumstance alone they are 
considered to be organic products, the residuum being 
regarded as the cell, and the earthy matter the cell-con- 
tents. The crystalline form, in these cases, is attributed 
to “the animal cell not having sufficiently controlled the 
mode of deposition of the earthy particles, they have, in 
consequence, assumed the crystalline form.” I may ob- 
serve, that, in globular calculi, containing a large propor- 
tion of triple phosphate, when im a state of molecular dis- 
integration, in consequence of bemg kept in a denser 
medium than that in which they were formed, almost the 
same kind of crystals are produced. See article, ‘ Com- 
plete Molecular Disintegration.’ The particular structure 
named by Dr. Carpenter, “ prismatic cellular substance,” 
found in some parts of the shell of the Pinna, and about 
the edge of the shell of the oyster, forms no exception in 
its mode of formation to that of the other parts of these 
shells. But, on the contrary, if examined in a sufficiently 
early stage of development, it will be seen to present ap- 
pearances as indicative of molecular coalescence as any 
other shell-tissue. This substance occurring in the softer 
and more membranous shell-tissues, where the globular 
particles are not exposed to pressure on all sides, as in the 
hardest parts, and, therefore, flattened out into scales, 
is only pressed laterally by the adjacent globules, and, 
therefore, flattened only on the sides where they he in 
contact, the parts of these globules which are free retain- 
