by the manner in which they reciprocally sympathise with each other-so long as we perceive the powers of the mind augmenting with health, and diminishing with disease-so long as we observe that the mind is incapable of occupation when the body is wearied by violent exercise, and in its turn unfitted for exercise, when the mental powers are fatigued by over exertion of the former-we can arrive but at one conclusion, that the balance of health can be maintained in its natural equilibrium only when mental exertion is proportioned to bodily activity. When this is not the case literary fame is dearly purchased; and all the glory that surrounds it cannot make amends for the health that has been sacrificed for its attainment. "On est trop savant quand on l'est au depens de sa sante; a quoi sert la science sans le bonheur???

In conclusion, there are a few words of Tissot's which serve the purpose of a summary of the preceding observations. To comprehend the influence of mental labour on physical. health, it is only necessary to remember, in the first place, that the brain is in aetion when one thinks; secondly, that the tendency of continual -action is to produce fatigue, and that fatigue

deranges the functions, because every debilitated

organ performs its duties imperfectly and irregularly; thirdly, that all the nerves proceed from the brain, and precisely from that part of it which is the organ of thought, the common sensorium; fourthly, that the nerves are one of the most important parts of the human machine, that they are necessary to every function, and that when once their action is deranged, the whole animal economy suffers from that derangement.

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CHAPTER IV.

THE NERVOUS ENERGY.

BUT what is this subtle fluid which exerts so wonderful an influence over mind and body? Under how many names has the knowledge of its nature baffled human inquiry in all ages! and how ignorant still are we of its essence! still is it known to us only by its effects.

We feel when the nervous energy abounds that every thing is well with us; we find when it is deficient that we are depressed; we know if it is exhausted that we become debilitated; and if suddenly destroyed, that death must immediately ensue !

Is it then the vital principle, or the cause of it-or is it indeed the cause of that effect which Brown mistook for animation, when he asserted that irritability was life itself? Motion, no doubt, is the grand characteristic of life; but motion is only the consequence of irritability. The propulsion of the blood is immediately caused by the irritability of the muscular fibres of the heart and its channels; but nature accomplishes

all her phenomena by physical agency. To what agent, therefore, are we to refer this irritability, before we arrive at the ultimate cause of lifethat causa causarum which is God! Is it to electrical agency we are to look for the solution of the mystery? or is there any thing analogous to the principle of life in the phenomena of the electric fluid? The nervous energy, however, is so much a part and parcel of the vital principle, their union is so intimate, that whether they stand in the relation of cause and effect, or are different names only for the same essence, they cannot be separately considered. The few observations that follow are not altogether irrelevant to the subject of these pages, nor is there any thing beyond the range of legitimate inquiry, in the consideration of the nature of that power which is the source of animation. Were we, indeed, to jump at the summary conclusion, that life is the sum total of the functions, as some have asserted, we should fall into the error of mistaking a subordinate effect for an original cause; forgetting, that although life is co-existent with the developement and cessation of these functions, it is the nervous energy which calls them into action. Whatever be its nature, it is yet an intermediate link, evident, though not obvious in that perpetual chain of cause

and effect which is the connecting medium between animation and the great Author of it.

"The first link of that chain," says Darwin, "is rivetted to the throne of God, dividing itself into innumerable diverging branches, which, like the nerves arising from the brain, permeate the most minute and most remote extremities of the system, diffusing motion and sensation through the whole.

"As every cause is superior in power to the effect which it has produced, so our idea of the power of the Almighty Creator becomes more elevated and sublime, as we trace the operations of nature from cause to cause; climbing up the links of those chains of beings, till we ascend to the great source of all things."

The doctrine which would have us suppose that this wonderful machine, the human frame, originated in a fortuitous concourse of atoms, has its error in failing to trace the causes of the combination of matter to their remote origin, and therefore chaos and its products are to this system what nature and the results of her wellordered designs, are to true philosophy. The doctrine we allude to confounds the attributes of mind with the properties of matter, by referring the mental faculties to the aggregation of the functions of the body. This is not only