BY MOLECULAR COALESCENCE. ldo 
should be formed on different principles, it would appear 
much more so, if these two opposite principles were em- 
ployed at the same time in the formation of different parts 
of the same integument, this could not fail to be the case in 
the skins of those reptiles, which, as in the toad, contain 
in some parts, carbonate of lime, resembling shell, whilst 
in other parts this substance is entirely absent. See a 
paper of mine on the Skin of the Toad in the ‘ Micro- 
scopical Journal.’ I may notice here, that this explana- 
tion is intended to apply only to the histology of tissues, 
and not to their physiology; that is, to the manner in 
which they are formed, and not to the manner in which 
they act. ‘To take im illustration of my meaning the three 
kinds of corpuscles—the common mucous corpuscles, the 
ciliated mucous corpuscles, and the cerebral corpuscles, I 
may observe that, although I consider each kind to aec- 
quire its form by the operation of the same physical 
force, and that this force, in all of them, acts exactly 
in the same manner, I do not by this intend to imply, 
that the function of each, whether obscure or patent, is 
necessarily a physical phenomenon,—this is not a part of 
the subject-matter of these researches. However, if the 
cause of these phenomena is physical, it is certain that 
the manner in which they are produced would require for 
its comprehension a knowledge of the different depart- 
ments of physical science,—chemistry, electricity, and 
the molecular condition and capabilities of matter more 
refined and more extensive than is at present possessed by 
philosophers. And as life, considered abstractedly, is 
altogether incomprehensible by our senses, it is probable 
that all future advances in physiological science will be little 
more than fresh disclosures or clearer views of physics and 
the sciences therewith associated, as connected with orga- 
