Fig. 3.

The results obtained were as shown in figs 4, 5 and 6, that sometimes a rise took place during the inhalation, but generally a sinking, much less however than in the normal condition.

We may therefore conclude that the diminution in the bloodpressure is not due to weakening of the heart's action, but to a dilatation of the vessels, and that this depends on the ac

Fig. 4.

- Inhalation begun.

* Inhalation stopped; at the beginning of the last three observations the Aorta was compressed. o Aorta opened.

tion of the nitrite on the walls of the vessels themselves. Whether this is due to its action on the muscular walls themselves, or the nerve-ends in them, cannot at present be with certainty said; and further experiments must be made to determine whether the walls of the arteries are the only structures consisting of unstriped muscle which are affected by it.

In the last four observations the aorta was compressed; at o the aorta was opened. Inhalation begun. + Inhalation stopped.

The further dilatation which takes place after the usual tone of the vessels has been destroyed by division of the cord, seems to indicate that it is of an active nature analogous to that in the vessels of the penis after irritation of its nerves; and this would point rather to an affection of the nerves than of the muscular fibres. In conclusion, I desire to express my warmest thanks to Professor Ludwig for the great kindness he has shown me, and for his invaluable advice and assistance in this investigation.

The ordinates indicating the pressure, begin 50mm. above the abscissa. spinal cord was divided; the aorta compressed, at o the aorta was opened. stopped.

In the last three observations the – Inhalation begun. + Inhalation

THE PHYSICAL RELATIONS OF CONSCIOUSNESS

AND THE SEAT OF SENSATION, A THEORY
PROPOSED. BY PROFESSOR CLELAND, Galway.

[Read at the British Association Meeting at Liverpool.]

IN venturing to disturb the theory of Sensation as it has long been taught, I am very sensible that it may be difficult to obtain a patient hearing, seeing that it is a theory universally received; yet there are important points which that theory leaves unexplained, points familiar to all, and which only require to be mentioned for every one to admit, that as the theory at present stands, they are totally inexplicable. That theory may be shortly stated thus:-that an irritation applied in the neighbourhood of a nerve-extremity produces an impression which is conducted along the nerve till it reaches the seat of consciousness in the brain; and that the mind, affected by the impression, becomes thereby cognisant of a sensation, which it refers to the extremity of the nerve along which the impression has been conducted. Further, let it be recollected that nervous impression is nothing but a physical condition, some of the peculiarities of which have been laid bare by experimenters, and which is capable of affecting any of the nervous elements, viz. nerves, both motor and sensory, and nerve corpuscles.

In speaking of nervous impression thus defined, we deal with a matter of fact, although we are not thoroughly acquainted with its details; but in stating the doctrine of the modus operandi of sensation we have merely to do with a theory.

This theory is, however, a physiological as well as psychological theory, and involves the consideration of the functions of nervous structures, as well as the laws to which consciousness is subject; and I am all the more anxious to point this out, because the physiologist is liable to think that where consciousness is involved physiology cannot be concerned, whereas the doctrine of sensation, although it relates to a matter on the psychological frontier, is arrived at from physiological data— and it is because it is, as I hope to shew, at variance with