184 
Referring to that series of bones, which seems to approximate the 
nearest to the entrochi, I mean the vertebrae, to the diseases of which, 
in the human body, particular attention has been paid, two most 
prominent facts are observable. The one is, that in every disease of 
these parts in which the substance of the bone has been so materially 
affected, as to have been rendered unfit for motion, the articulating 
surfaces anchylose together, so that the morbidly tender parts are 
no longer liable to injury by motion. The other fact is, that as 
these parts, weakened by disease, must, of course, be less capable of 
supporting the weight naturally imposed on them, an exudation of 
lymph is thrown out, in which is deposited that portion of earthy 
matter which is necessary to the constitution of callus. By this pro- 
cess, the consequence of injury and of inflammation of these parts, 
the requisite degree of support is obtained, although the motion imme- 
diately belonging to these parts is lost. 
The specimen to which I have called your attention bears indubitable 
marks of these entrochi having been the subjects of both these processes. 
The naked eye at once sees, in that part of the straight column 
which is uncovered, an unnatural state of the trochitse or vertebrae : 
their forms are not similar, nor are their lines of articulation regular. 
By a closer inspection, especially with a magnifying glass, it may 
also be discovered that the processes forming the crenulated edge 
have been removed, and that a line onlj'^ slightly undulated, marks 
where the articulation existed, and shews plainly such a species of 
connection between the trochitae as must have occasioned a complete 
anchylosis. 
Equally positive is the evidence in favour of the substance, in 
which these entrochitae are involved, being produced by the powers 
of restoration possessed by the animal. Its colour, its texture, and, 
indeed, its general appearance accord so exactly with those of the 
entrochi themselves, as to render it indubitable that it has proceeded 
from a similar organization. 
