OSTEOCOLLA, ὀστεοκόλλα, in Natural History, a white or ash-coloured sparry substance, in shape like a bone, and by some supposed to have the quality of uniting broken bones. It is found in long, thick, and irregularly cylindrical pieces, which are in general hollow, but are sometimes filled up with a marly earth, and sometimes contain within them the remains of a stick, round which the osteocolla had been formed. But though it is plain that many pieces of osteocolla have been formed by incrustations round sticks, yet the greater number are not so; in fact, they are irregularly tubular, and appear to be formed of a flat cake, rolled up in a cylindrical shape. The crusts of which these are composed do not form regular concentric circles round the internal cavity, as must have been the case had they been formed by incrustation. On the other hand, they plainly show that they were once so many thin strata, composing a flat surface, which has afterwards been rolled up, as one might do a paper three or four times doubled, into two, three, or more spiral lines. In this case, each single edge of the paper would be everywhere a regular point of a continued spiral line drawn from a given point; but they would by no means be so many detached concentric circles. The osteocolla is found of different sizes, from that of a crow-quill to the thickness of a man's arm. It is composed of sand and earth, which may be separated by washing the powdered osteocolla with water, and is found both in digging and in several brooks, in many parts of Germany and elsewhere. In some parts of Germany it is called hammosteus, from its always growing in sand, never in clay, or any solid soil, nor even in gravel. Where a piece of it anywhere appears on the surface, they dig down for it, and find the branches run ten or twelve feet deep. They usually run straight down, but sometimes they are found spreading into many parts near the surface, as if it were a subterranean tree, the main stem of which began at twelve feet depth, and thence grew up in a branched manner till it was met by the open air.
The osteocolla found in the earth is at first soft and ductile, but in half an hour's time, if exposed to the air, it becomes as hard as we find it in the shops. The method of taking up a perfect piece for a specimen is to open the ground, clear away the sand, and leave it so for an hour or thereabouts, in which time it will harden, and may be taken out whole. It is certain that the osteocolla is produced at this time; for if a pit be cleared of it, more will grow there in a year or two, only it will be softer, and will not harden in the air so easily as the other. What the rotten substance resembling the decayed branches of trees is, we cannot determine, unless it really be such; but the opinion of the common people, that it is the root of something, is absurd, because its thickest part lies at the greatest depth, and the branches all run upwards. The osteocolla is a marly spar which concretes round this matter; but what it is that determines it to concrete nowhere on the same ground excepting around these branches, it is difficult to say. The rottenness of this substance, which forms the basis of the osteocolla, renders it very liable to moulder and fall away, and hence it is that we usually see
the osteocolla hollow. Sometimes it is found solid; but in this case some vegetable matter has served as its basis, and instead of one branch, it will be found to have concreted about a number of fibres, the remains of which will be detected in it on a close examination.