Page:Proceedings of the Royal Society of London Vol 2.djvu/43

Rh heart's action in carp, after being fully exposed by opening into the pericardium without any injury being done to the brain or spinal marrow, Mr. Clift next passed a hot wire from the tail to the occiput of a carp of the same size, so as to destroy its spinal marrow; and he found that the action of the heart was quickened for two or three beats, but then resumed the same rate of pulsation as before, although the voluntary muscles had lost their power and did not contract when a stimulus was applied to them.

After several repetitions of this experiment, with various modifications in the mode of conducting it, the author arrives at the following results:—

1st. That the muscles of the body of a carp can be thrown into powerful action four hours after the brain and heart are removed.

2dly. That those muscles lose all power as soon as the spinal marrow is destroyed.

3rdly. That by exposure of the heart to water in which the fish is allowed to swim, the action of the heart ceases sooner than in air.

4thly. That whether the heart is exposed or not, its action continues long after the brain and spinal marrow are destroyed; and still longer when the brain is removed without previous injury to its substance.

5thly. That the action of the heart is in general accelerated for a few beats by injuries to the brain or spinal marrow; but that destroying the spinal marrow after the brain has been separated renders the action of the heart slower for a few beats. 



Beside the use which may be made of what remains of ancient paintings as models for imitation, the author has endeavoured to reap the further advantage of making us acquainted with the nature and chemical composition of their colours; for though the works of Dioscorides, Vitruvius, and Pliny contain descriptions of many substances used by the ancients as pigments, it is only by experiment that the subjects of which they speak can be identified.

The author's experiments have been made upon colours found in the baths of Titus, in the ruins called the baths of Livia, and other ruins of ancient Rome, and in the ruins of Pompeii. Some of these colours had been discovered in vases beneath the ruins of the palace of Titus, and were found to be the same as those used in various fresco paintings of the palace. In one large vase, discovered about two years since, there were found, among other colours, three different kinds of red, one approaching to orange, another dull red, and a third purplish red. The first was minium, the second and third proved to be both ochres of different tints. Another red found in various fresco paintings differed from those found in the vase, and proved to be vermilion. This substance, called by the Greeks, was known