force has been ascertained by experiment to bear a very striking resemblance to electricity, though its difference is also evident. A feeble galvanic current transmitted along the motor nerve of an animal recently killed will produce muscular contraction; whilst, on the other hand, a similar current transmitted along an afferent nerve will excite reflex movement through its ganglionic centre. "However strongly we may be convinced of the absence of identity between nervous and electric forces, it is impossible to be otherwise than impressed with the extraordinary analogy which exists between them. To use Professor Grove's term, they are mutually correlated, and that in the closest degree." Heat, in like manner, if applied to a motor nerve in its course, calls forth muscular contractions, and if applied to a sensory nerve it will occasion sensations, both common and special, precisely after the manner of electricity.

The same may be said of chemical affinity; for if certain reagents be applied to nerve-trunks they may be made to call into action their various endowments, whether these be motory or sensory; whilst, on the other hand, there is ample evidence that the chemical properties of secretions may be greatly changed under the direct influence of nervous force."

In the brute, every impression through a sense produces a corresponding muscular discharge. We can thus complete the circle. But with man-and the brute which has cerebral hemispheres, and uses them in accumulating ideas. -the circle is as yet incomplete. We can trace, say, the force of the impact on the retina of scarlet waves to the

1 Dr. Carpenter on Mattrucci's Lectures, in Medico-Chirurgical Review, 1848.

2 Philosophical Transactions, vol. cxl. (1850), p. 745.

brain, but we see no corresponding liberation of this force. It is therefore taken up, and becomes latent, just as the solar force has become latent in the beds of coal, and is only liberated when the coal is burnt. The force from the stroke of the waves of scarlet light is taken up by the brain, and there becomes an idea. In the formation of the idea the force becomes passive.

Where there is no perception, there is no idea to answer to it. The man blind from his birth can form no conception of scarlet; for the optic ganglia have not been charged with the force which forms the idea of scarlet, and ex nihilo nihil fit applies to ideas as well as to material objects.

Thus we can form no ideas of that which we have never seen, heard, smelt, or tasted.

Idealization is the accumulation of remembrances-that is, of fossil percepts and the using of them up; if this ideal be not spent, it remains in the brain. Say it is an ideal of beauty: the sculptor elaborates it in marble, and runs the pent-up force out of his brain.

In the beast whose action is sensori-motrix, this action is what is generally called instinctive: no reasoning takes place; the creature receives an impression which becomes a sensation, and acts blindly on it. But in man, the sensation is transmitted to the great hemispherical ganglia, or cerebrum, and is there idealized and registered. Perception is the portal to intellectual action; for while in sensation the conscious mind feels intuitively the physical impulse of the outward object as it affects the consciousness through the sensorium, in perception the nervous impression is carried a stage farther, and, by virtue of the harmony which exists between the percipient mind and the external world, the sensory impression is intuitively translated into

the form of intelligence, and becomes an intellectual phenomenon. If we reflect on the processes that go on in our own minds, we easily distinguish between a sensation and an idea, and are able to mark the sequential origin of the latter. We often hear words, but they convey no idea to our minds for some minutes, when all at once their significance breaks upon us. The correlated physiological phenomena may be thus stated: The auditory ganglia receive the sentient impression at once; its passage onward is delayed; presently, however, the obstruction is removed, the sensation flows into the hemispheric ganglia, oxidation takes place, and the ideas are formed corresponding to the words received by the ear.1

A schoolmaster complains that his boys will not pay attention to their lessons. The vital force of the children is at the time engaged upon the digestion of raw apples, robbed from the master's garden. If a portion of the skull of one of these urchins were removed, the brain would be found to be almost colourless, and by no means filling the cavity of the cranium. Let, however, this boy suddenly resolve to apply his mind to the task: instantly a delicate rosy flush will appear over the surface of the cerebrum; it will swell and protrude from the opening. The vital energy has jerked the blood from the coats of the stomach into the veins of the head.

The sensory ganglionic tract is, as has been said, the seat of the emotions. Man has the power, shared with him by some of the higher Vertebrata, but by them in a vastly inferior degree, of resolving an idea into an emotion-that is, of fixing his affections on some conception of the cerebrum. He forms an idea not always out of immediately

1 Noble Correlation of Psychology and Physiology, p. 27; and Dunn: Physiological Psychology.

:

received impressions, and this idea he transmits to the thalami optici, where it becomes an object of emotion; the corpora striata and the cerebellum share in the agitation, and the muscular action expends the force. Thus, I see an object the perception becomes one of danger; my emotion of fear is aroused, and contraction of the heart and cessation of breathing ensue. Or I call up ideally some image of beauty: the emotion of love is excited, muscular action is again set up, and the heart beats rapidly and the breath comes short and quick.

The importance of the cerebral hemispheres to man cannot be questioned. As the seat of intelligence, they place man above the brute, the European above the red-skin, and the red-skin above the negro. In the European the cerebrum is far larger than in the red-skin and negro; and this is due, possibly, to a long training, which has developed cerebral cells at the expense of cerebellic cells. The redskin depends for subsistence on his agility, and therefore his vital energy labours to perfect the cerebellum, in which co-ordination of muscular action takes place. But it is not so with the European; he depends on the activity of his intelligence, and therefore the energizing principle enlarges the amount of cerebrum, and deepens its convolutions. We all know by experience that the exercise of muscle tends to strengthen it; that is, the direction of the attention of our vital energy is devoted to the construction of muscular fibre. We know that education sharpens the wits; that is, the same vital energy is turned to the elaboration of brain matter. We know also by experience that in proportion as we use up acquired force in muscular exertion intellectual action fails, and in proportion as mental work is executed does muscular power languish.

We will not consider the importance of intellect, which

is admitted by all, but the importance of emotion, or feelings, which some are disposed to underrate.

The feelings are the great incentives to intellectual activity. They register pleasure and pain. Certain sights and sounds afford them gratification, and they urge the intellect to seek out modes of reproducing those impressions. Other sights and sounds distress them, and they excite the intellect to devise methods of avoiding them. The feelings seem to be tuned in a definite key, and certain undulations of sound or of light set them in rhythmical harmonious vibration, whilst others throw them into discordant agitation.

Without the feeling of pleasure derived from study there would be no intellectual advance among mankind; without that of domestic love there would be no association; without the feeling of delight produced by harmonies of shape, colour, and sound, there would be no art.

The emotions are indeed the spring of intellectual activity, and their development is as essential to man's well-being and pre-eminence as is that of his reasoning powers. And, as the reasoning powers can be directed towards any one point, or on any one subject, so can the affections take one direction to the exclusion of other directions. The emotions and thoughts are so closely connected that they usually work together; but occasionally they are in antagonism, as when the desire tends towards what the reason knows to be unadvisable. "The passions," said Sydney Smith, "are, in morals, what motion is in physics: they create, preserve, and animate; and without them, all would be silence and death. Avarice guides men across the deserts of the ocean; pride covers the earth with trophies, mausoleums, and pyramids; love turns men from their savage rudeness; ambition shakes the very foundation of kingdoms. By the love of glory, weak nations swell