Page:Proceedings of the Royal Society of London Vol 1.djvu/534

Rh portions of blood to be supplied to diﬂ'erent parts of the body. The facts which ﬁrst led the author to entertain this opinion, were the accidental consequence of an extremely painful application of pure kali to a wound, which occasioned a general pulsation of the limb to which it was applied, although the pulsations of distant arteries were at the same time undisturbed. In order to be quite certain that this consequence was really dependent on the irritation of nerves, the author made two experiments on rabbits in the neighbourhood of the carotid artery. Having laid bare the par vagum and intercostal nerves, a probe was passed under the former so as to separate it, so that the irritation might be ﬁrst given to this nerve alone; but no sensible effect was thus produced upon the artery. But when the same ap- plication of pure kali was made to the adjacent intercostal nerve. by which the artery is supplied, the dilatations and contractions of the artery were considerabl increased, and the violence of the pulsations continued about three motes bef they began to subside.

The same experiment 'being repgeted n a second rabhit, was at- tended with the same esult; and it W afterwards repeated on a dog without any perceptible diﬂ'erence.

These visible effects of the inﬂuence which the nerves possess over the arteries, enable the author to comprehend, more fully than he had done before, how dilferent supplies of blood are sent to particular glands; how various secretions come under the inﬂuence of the mind, and how the internal actions of the animal economy, connected with the circulation of the blood, are regulated.

If the healthy actions in the complete animal be thus dependent on nervous inﬂuence, then also the restoration of parts injured, the regeneration of parts lost; and all, even the most complicated forms of disease, must be regulated by the natural or pretematural operation of the same machinery.

When steam is passed through a tube surrounded with water, it is well known that it becomes condensed on the sides of the tube so long as the water continues at a lower temperature than that of the steam ; but since the latent heat given out in the condensation of steam soon raises the temperature of the water to 212", all transfer of heat ceases at that temperature, and the steam then passes uncondensed. But since the temperature at which water may be raised into vapour depends on the pressure of the atmosphere, the temperature of the surrounding water may be kept permanently lower, by removing that pressure, so as permanently to act in condensing the vapour of the ﬁrst distillation; and being itself raised into vapour by mere transfer of the same original quantity of heat, may be received as an additional product of the same process, by a suitable arrangement of the apparatus.