Observations on the Functions of the Brain. By Sir EVERARD
HOME, Bart.-[1815.]

BEFORE I enter into the particular effects that take place when pressure is made upon the brain by means of water, it is necessary to mention, that sudden pressure of any kind upon the cerebrum takes away all sensibility, whether made upon the external surface through the medium of the dura mater, or upon the internal parts through the medium of the ventricles, and sensibility returns as soon as the unusual pressure is removed.

Although insensibility is the common effect of undue pressure upon the cerebrum, it appears, from what will be stated, that it is not a necessary consequence of undue pressure upon the cerebellum.

Concussion of the brain produces delirium and coma; these symptoms may go off, and yet, sometimes, in a few days return and prove fatal. In the torpid state commonly attendant upon any violent shake being given to the brain, the senses are so ,much impaired, that little information can be gained respecting the effects produced upon the internal organs.

Sudden dilatation of the blood-vessels of the cerebrum, in consequence of exposure to the sun, is sometimes accompanied by delirium, loss of speech, and the power of swallowing. A dilated state of the veins of the cerebrum has been attended with head-aches, which are very severe when the body is placed in a horizontal posture.

When the smaller arteries of the cerebrum are preternaturally enlarged, while those of the cerebellum are not, delirium has taken place, followed by a fit resembling apoplexy, and a paralytic affection of one side.

An obstruction to the passage of the blood through the right internal carotid artery, was attended by a succession of slight apoplectic fits, unaccompanied by any paralytic affection.

A deep wound into the right anterior lobe of the brain, attended with inflammation and suppuration, produced no sensation whatever; the senses remained entire, and the person did not know that the head was injured.

The brain shooting out in the form of fungus, after the dura mater is wounded, has no effect upon any of the nerves, nor is it attended with sensation; but the inflamed pia mater gives great pain.

Loss of a portion of the medullary substance of the anterior lobe of the cerebrum, produced no symptoms. Loss of a

portion of one of the hemispheres was attended with difficulty of swallowing for twenty-four hours, and slight delirium of short duration. Ulceration of the anterior lobe of the brain, as low as the anterior cornu of the lateral ventricle, but not communicating with it, was attended with paralysis of both

arms.

In a case of a penetrating wound into the right hemisphere of the brain, with bone forced into its substance, while there was an opening for the discharge of matter, no effects were produced, except when the circulation was much increased; and then only head-ache and numbness in the left side.

Pressure upon the medulla spinalis in the neck, by coagulated blood, produced paralytic affections of the arms and legs; all the functions of the internal organs were carried on for thirty-five days, but the urine and stools passed involuntarily.

Blood extravasated in the central part of the medulla in the neck, was attended with paralytic affection of the legs but not of the arms.

In a case where the substance of the medulla was lacerated in the neck, there was paralysis in all the parts below the laceration; the lining of the oesophagus was so sensible, that solids could not be swallowed, on account of the pain they occasioned.

Where the medulla in the back was completely divided, there was momentary loss of sight, loss of memory for fifteen minutes, and permanent insensibility in all the lower parts of the body. The skin above the division of the spinal marrow perspired; that below did not. The wounded spinal marrow appeared to be extremely sensible.

On the Nature and Cause of the Pulse. By Dr. PARRY.

DR. P. takes a review of the different theories which have been proposed to account for the phenomenon of pulsation, observing that the greater part of physiologists had contented themselves with the opinion of Haller, that pulsation was occasioned by the diastole and systole of the heart.

His view, however, of the question is much simpler; on examining different arteries where they were exposed to no obstruction or pressure, he found that they had no pulse: by pressing the finger on an artery over a soft part of the body, which yielded sufficiently to the pressure, no pulse was manifested; but whenever an artery was pressed over a solid part, then a pulse was immediately found. He repeated these operations several times, and uniformly found the same effects.

Hence he concludes, that the pulse is nothing more than the re-action or impetus of the blood to maintain its regular motion. The arteries appear only as canals through which the blood flows in a uniform and continuous current: dimi nish the diameter of the canals, and a pulse is immediately perceived. At every junction of a vein with an artery, the internal diameter of the latter is diminished, and hence a pulse always appears.

Experiments and Observations on the Colours used in Paintings by the Ancients. By Sir H. Dávy. — [1815.]

THE works of Theophrastus, Dioscorides, Vitruvius, and Pliny, contain descriptions of the substances used by the ancients as pigments; but hitherto, I believe, no experimental attempt has been made to identify them, or to imitate such of them as are peculiar. The experiments of this philo sopher have been made upon colours found in the baths of Titus, and the ruins called the baths of Livia, and in the remains of other palaces and baths of ancient Rome, and in the ruins of Pompeii. He was enabled to select with his own hands specimens of the different pigments that have been found in vases discovered in the excavations lately made beneath the ruins of the palace of Titus, and to compare them with the colours fixed on the walls, or detached in fragments of stucco; and he was allowed actually to make experiments upon the colours of the celebrated picture "Nozze Aldobrandine;" but he adds, "When the preservation of a work of art was concerned, I made my researches upon mere atoms of the colour, taken from a place where the loss was imperceptible and, without having injured any of the precious remains of antiquity, I flatter myself I shall be able to give some information, not without interest to scientific men as well as to artists, and not wholly devoid of practical applications."

Of the Red Colours of the Ancients. Of these, three species are mentioned; one bright and approaching to orange; another dull-red; and a third, a purplish-red. On exposing the bright-red to the flame of alcohol, it became darker-red; and on increasing the heat by a blow-pipe, it fused into a mass having the appearance of litharge, and which was proved to be this substance by the action of sulphuric and muriatic acids: this colour is consequently minium, or the red oxide of lead. By other processes, which are particularly described, he found that the dull red colour is an iron ochre,

and the purplish-red was proved to be an ochre of a different tint.

In examining the fresco-paintings in the baths of Titus, he found that these colours had been all used, the ochres in particular, in the shades of the figures, and the minium in the ornaments on the borders. He found another red on the walls, of a tint different from those in the vase, and much brighter, and which had been employed in various apartments, and formed the basis of the colouring of the niche, and other parts of the chamber in which the Laocoon is said to have been found: this proved to be vermilion or cinnabar; for, on heating it with iron filings, quicksilver was -procured.

In the picture already mentioned, the "Nozze Aldobrandine," the reds are all ochres: on these reds the action of acids, of alkalies, and of chlorine could discover no traces either of minium or vermilion in the picture..

Of the Yellows of the Ancients. A large earthen pot, found in one of the chambers of the baths of Titus, contained a quantity of yellow paint, which, when submitted to chemical examination, proved to be a mixture of yellow ochre with chalk. There were three different yellows; two of them proved to be yellow ochres mixed with chalk in different proportions; and the third, a yellow ochre, mixed with red oxide of lead or minium.

Of the Blue Colours of the Ancients. — Different shades of blue are used in the different apartments of the baths of Titus, and several very fine blues exist in the mixtures of their colours. These blues are of different hues, according as they contain larger or smaller quantities of carbonate of lime; but, when this carbonate is dissolved by acids, they present the same body colour, a very fine blue powder, similar to the best smalt or ultramarine, rough to the touch, and which does not lose its colour by being heated to redness; but which becomes agglutinated and semifused at a white heat.

Of ancient Greens.-The deep sea-green colouring matter, taken from the ceiling of the chambers called the baths of Livia, proved to be soluble in acids, with effervescence; and when precipitated from acids, it was re-dissolved in solution of ammonia, giving it a bright blue, produced by copper. There are several different shades of green employed in the baths of Titus, and on the fragments found near the monument of Caius Cestius: there were three different varieties; one, which approached to olive, was the common green earth of Verona; another, which was a pale grass green, had the

character of carbonate of copper, mixed with chalk; and a third, which was a sea-green, was a combination of copper mixed with the blue copper frit.

Of the Purple of the Ancients. This was regarded as their most beautiful colour, and was prepared from shell-fish. According to Vitruvius, the colour differed according to the country from which the shell-fish was brought; that it afforded a colour deeper and more approaching to violet from the northern countries, and a redder colour from the southern coasts. The finest purple had a tint like that of a deep-coloured rose; and in painting, it was laid on to give the last lustre to the sandyx, a composition made by calcining together red ochre and sandarach, and which, it is inferred, must have been nearly the same as our crimson.

An Account of some Experiments with a large Voltaic Battery. By J. G. CHILDREN, Esq. F.R. S. —[1816]

THE copper and zinc plates of this apparatus are connected together in the usual order by leaden straps; they are six feet long, by two feet eight inches broad, each plate presenting 32 square feet of surface. All the plates are attached to a strong wooden frame, suspended by ropes and pulleys, which, being balanced by counterpoises, is easily lowered and elevated, so as to immerse the plates in the acid, or raise them out of it at pleasure.

The first trials of the power of this instrument were made in July 1813, in the presence of several philosophical friends; but the effects then fell very short of my expectations, arising, as I afterwards found, from a defect in the construction, which has been since remedied, and another copper-plate added to each member of the series, so that every cell now contains one zinc and two copper-plates, and each surface of zinc is opposed to a surface of copper.

The battery was moderately excited by a charge of one part acid, diluted with 40 parts of water.

Exp. 1. A platina and a gold wire being connected and introduced into the electrical circuit, the platina was instantly ignited; the gold remained unaffected.

Exp. 2. A similar arrangement of gold and silver wires. The gold was ignited, the silver not.

Exp. 3. The same with gold and copper. No perceptible difference in the state of ignition; both metals were heated red.