ther by ligament, and. forming a tube communicating from one extremity of the spine to the other.
This species of intervertebral joint, which thus appears common to the fish tribe, is not found to obtain in the whales, as their structure in this, as in many other respects, is the same as that of quadrupeds, but is more distinctly visible, from the vast size of the parts. In them the intervertebral substance is arranged in concentric circles, connected by transverse fibres, the external layers being very firm and compact; but the interior become successively softer, till in the centre there is a soft pliant substance, more like jelly than an organized body, corresponding in its use to the incompressible fluid in fish.
In the bullock, sheep, deer, monkey, and man, the structure cor- respomk with that of 'the whale ; but in the hog and rabbit a cavity was observed, with a smooth internal surface extending through half the diameter of the vertebrae; so that the structure in these animals imitates that of fishes, though not for any obvious purpose.
In the alligator the several joints are regularly articulated with capsular ligaments, and are lubricated with synovia. In the snake there is a regular ball and socket joint between every two vertebrae; so that the means employed for the motion of the back-bone in different animals, comprehends almost every species of joint.
Mr. Home's paper has annexed to it an appendix, by Mr. William Brande, giving an account of the chemical analysis of the fluid contained in the intervertebral cavity of the Squalus mnzimus.
Its specific gravity was found to be 1027. It was not coagulated by heat.
No precipitation was occasioned by infusion of galls, or of catechu; nor was any change produced by alcohol.
But oxymuriate of mercury, muriate of tin, nitrate of silver, and acetate of lead, threw down copious precipitates.
From the effect of these re-agents, it appears to Mr. Brande, that ‘the fluid contains neither gelatine nor albumen; but when the fluid was evaporated to half its bulk, pellicles began to form on the Sur- face, indicating the presence of a variety of animal matter, which the author considers as mucus or mudlage, but which, under certain cir- cumstances of evaporation, is capable of being converted into a mo- dification of gelatine or albumen.
Until a portion of platina was lately discovered by M. Vauquelin, in some silver ores from Estremadura, the whole of the platina known in Europe was derived from the Spanish possessions in South America, and had very uniformly the same appearance, differing solelyin the magnitude of the grains.
A third variety having lately been received from Brazil, the author
