Obs. Among the most remarkable of the recent discoveries in chemistry are those of MM. Wohler and Deville, relative to silica and boron. Each of these substances is now proved to exist in three very different states, analogous to the three known states of carbon, namely, charcoal, graphite, and diamond. The last of these states is, of course, the most interesting. Crystallised boron possesses a hardness, brightness, and refractive power comparable to those of the diamond; it burns in chlorine, without residue, and with circumstances resembling those of the combustion of diamond in oxygen; it is not acted on by any of the acids, and appears to be the least alterable of all the simple bodies. Its powder is already used in the arts, instead of diamond-dust; and it seems not improbable that, when obtained by the chemist in crystals of a larger size, it may rival even the diamond as a gem.
Some late experiments by Wohler and Deville seem to have established the fact, that the so-called “graphitoidal” boron is really a boride of aluminium. Its formation on fusing aluminium with amorphous boron or boric oxide appears to take place more particularly when the heat applied is neither very strong nor long continued.
Boron, Terflu′oride of. See Fluoboric Acid.
BOTHRIOCEPHALUS CORDATUS. Leuckart was the first to describe this creature, which is a parasitic worm infesting the human intestines. It is, however, much more commonly met with in dogs than in man. The annexed engraving depicts—b, the head (back view), magnified five diameters; b′, upper part of body and head, magnified two diameters; a is a portion of the worm, natural size. See Bothriocephalus Latus.
BOTHRIOCEPHALUS LATUS. A parasitic worm infesting the human intestines. Although classed with the tapeworms, it differs essentially from tænia. The head is of an elongated
form, compressed with an anterior obtuse prominence into which the mouth opens.
The animal has the power of elongating and contracting the neck, so that it appears sometimes short, sometimes long. The joints or segments commence about three inches from the head; the anterior ones are nearly square, but the remainder are much elongated transversely. Each segment contains on its flat surface two orifices, the anterior connected with a male, the posterior with a female organ of generation. The parasite is of a brown colour, and from six to twenty feet in length.
Those who are affected by this worm never pass the single segments from the bowels, but void them in chains of many links. The ova are also frequently to be met with in the fæces; they are of an ovoid shape; the capsule is perfectly translucent, and the yolk is distinguishable. The yolk undergoes segmentation, and ultimately develops an embryo with six hooks at the anterior extremity, cased in a mantle studded with vibratory cilia, and the lid of the capsule then opens up; and the embryo escapes. If they do not obtain access to the intestines of an animal within a week, they lose their ciliated mantle and perish. Drinking-water is supposed to be the chief if not the only medium through which the parasite gains admissions to the intestines in man. It seems to be unknown in England, except when imported; but is common in Russia, Sweden, Norway, Lapland, Finland, Poland, and Switzerland.