est in the economy of life; - first, the relation of the nervous power to the proper vital contractility of the muscular fibre; secondly, the connexion of the voluntary and involuntary motions throughout the body. The former inquiries (founded on the distinction which Haller has not too strongly designated a lex æterna) have still left many points undetermined; such, for instance, as the proportion which the nervous and contractile powers respectively bear in all the various phenomena of muscular action, exhaustion, and intermission. These two powers are independent; originate in different sources; and may apparently exist at the same time in very different ratio to each other. The agent of stimulus through the nerves may be deficient, or exhausted by one set of actions; while the contractility of other muscular parts remains unimpaired. Or, as we have reason to suppose the nervous power is unequally generated at different times, it may occasionally be in excess above the muscular contractile power, which we know to be sometimes enfeebled generally throughout the body, by default of nutrition or other cause. The various combination of these circumstances (multiplied further by the distinction of voluntary and involuntary motions) is presumably a source of many singular results and anomalies, both in health and disease, which are not generally thus regarded; and I believe that more explicit attention to them under this view might solve many difficulties which still embarrass the subject.

that

The relation of voluntary muscular actions to those of involuntary kind presents questions as numerous, and equally complex in their nature. There are no more interesting topics of inquiry than the functions (such as respiration, deglutition, and the action of all the sphincters) in which both are concerned; and where, though commonly in concurrence, they are often found in opposition to, or impeding

each other. And a remarkable result of such inquiries is the evidence they furnish as to the limited and secondary nature of voluntary motions. Not only do these come last, and by aid of repeated effort and education; but they also soonest pass away under the influence of habit; especially in the case of the conjunction just described. The exercise which gives them highest perfection for use, does, in certain degree, remove them from that consciousness which seems essential to any just definition of the will; and the most distinct acts of volition are those in which muscles are brought into modes of exercise altogether new. Of the combined and complex movements which form the habits of life (for the action of a single muscle is comparatively rare) more cannot be affirmed, than that we will certain acts, which particular muscular combinations, wholly unknown to us in their details, are able to fulfil. It is a main business of physiology, in its present state of progress, to distinguish and better define these results; and what has already been done is an augury of conclusions more general than any yet obtained, and of certainty more complete in all stages of the research.

-

In closing this chapter (a mere outline of the inquiry) I may again remark that the topic is that to which all separate researches in physiology converge; blending themselves in this common centre on the one hand, with the higher doctrines of life, reproduction, and mental existence - on the other, with those great general powers or laws of inanimate nature which are ever in action within and around us. Physiological science, on the matter in question, seems at this moment to be on the verge of some greater discovery; resembling in this respect the actual state of other physical sciences those of light, heat, electricity, chemical forces, and perchance gravitation - which the course of modern inquiry

is ever tending to reduce to certain common laws. It is a question of deep interest, already referred to, whether the relation here is not closer than that of mere analogy; and whether future research may not associate some of the functions of the nervous system with the more general elements of force and action in the physical world. Vital laws, and what we term physical laws, stand precisely in the same relation to our knowledge. They are continually approximating as this knowledge advances; and may not impossibly in the end be submitted, even in human comprehension, to some common principle, embracing the whole series of phenomena, however remote and dissimilar they now appear.

All science tends to prove the unity of creation, through the evidence it affords of mutual and universal relation of parts. The expression of an eminent philosopher, "L'univers, pour qui sauroit l'embrasser d'un seul point de vue, ne seroit qu'un fait unique et une grande vérité," though in one sense it may seem a vague imagination, yet, in a larger scope of view, involves the great result and term of all philosophy. The "single fact" and "great truth," is that of one Almighty Cause; a conclusion to which we are irresistibly carried forwards from every side; surmounting in this inference those intermediate gradations of existence or power, which are too dimly seen to be rightly apprehended by the faculties of man in his present state of being.

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