THE

SECTION VII.

PHYSIOLOGY AND ETIOLOGY.

The Origin and Physiology of Nervous Force.

PAPER BY W. C. BARRETT, CHAIRMAN OF THE SECTION.

HERE are two things of which I wish to speak, and these two things make up the sum of the whole universe, so far as man can know. They are matter and force. I say the study of these must form the whole, the entirety of human research, so far as any positive knowledge, or the hope of definite information is concerned. We may speculate and theorize and dogmatize upon things spiritual and metaphysical as much as we like, but concerning them we can by no possibility arrive at any definite conclusion, nor can we prove any assertion, it matters little how wild it may be, as either absolutely true or false. When we come into the domain of physics we are studying the actual, the real, the tangible.

I desire, then, for a few moments to consider in a general way matter and force: the one real, positive, palpable, inert; the other immaterial, ethereal, incorporeal, yet dominative over the tactile mass-a law which is ever active in bringing about definitive changes in the passive matter; a ghostly, pervading something, which changes a dead, a lifeless, an inanimate mass of chaos, into this world of life and joy and beauty and animation.

What is this mysterious influence that we call force? Let us examine it. But in what I have to say I desire it ever to be borne in mind that I am speaking solely of physics, and that it has no kind of metaphysical or speculative application whatever. The relations of mind to matter it is no part of my present plan to endeavor to trace

out.

Force can be studied only through its chief resulting phenomenon-motion. We find that matter and force are infinitely opposed. Matter seeks eternal rest; force perpetual motion. They mutually react upon each other, matter being by force constantly changed in its characteristics; force by matter continually varied in

mode of manifestation. They are thus mutually interdependent, co-existent, eternal parts of one stupendous whole: interdependent, because one cannot form a portion of this universe without the other; co-existent, because each pervades the other, and eternal, because both can die only together. It has long been an axiom in physics that matter is imperishable. The same train of reasoning which proves this, establishes also the fact that force is indestructible. If an atom can change its condition only through the exertion of force, if its form only can be altered, the bonds which unite it to certain other atoms only be liberated to enable it to form new unions with yet other atoms, and yet if not one of those particles can be lost or annihilated, then can force, only by the reaction of matter, be induced to change its mode of manifestation or its direction. If not an atom has ever been destroyed since matter existed, then it necessarily follows that not an influence, not a wave of force has ever been extinguished since, simultaneously with matter, it first exerted sway. We may, through the action of force, alter the condition of matter; we may, through the reaction of matter, change the character of force; but both are alike indestructible and eternal. Matter is all one, under whatsoever form it may exist. Force is a unit, however it may manifest itself. These are predicates, truisms, selfevident, self-proved, fixed laws of physical science. This doctrine is not new, for as long ago as 1845 Faraday declared that he held the opinion that the various forms under which the forces of matter are made manifest have one common origin, and are so mutually interdependent that they are convertible one into another, and possess equivalents of power in their action. To my apprehension, matter and force are as intimately connected as are what Faraday calls the different manifestations of force with each other. We cannot conceive of matter except as it be subject to force. We cannot imagine power as distinct from the matter upon which it acts. They are essentially co-existent, coeval, synchronous.

Force may act upon matter in different ways, and the result may be motion of a mass, or of atoms. The changes consequent upon this action may be those of external form-morphological, or of internal structure-molecular. According to the peculiar manifestation of it we have been accustomed to call it heat, light, electricity, or chemical affinity; but in whatever mode it becomes sensible to our perceptions, there is one definition which will always describe it, one expression which always characterizes it: it is essentially matter in motion. Heat was formerly regarded as a subtle

substance, with unknown, tangible qualities, and its specific name was caloric. It was, with light and electricity, classed as an imponderable fluid, because it was conceived that no other hypothesis would account for the phenomena which they exhibited. Light, it was supposed, consisted of minute characteristic particles, which proceeded from the sun, or from any luminous body. Electricity, also, was regarded as an invisible entity of some kind, possessed of peculiar qualities. It was known rather by its physical manifestations than from any knowledge of its character, but the general opinion held it to be an extremely tenuous matter, which, while pervading most substances, could yet be bottled up, confined, or dissipated at will. It was usually spoken of as the electric fluid, and in my early school days I was taught that there were two kinds of electricity-a positive and a negative-which were always seeking to neutralize each other. Further study and investigation made manifest the absurdities of those crude theories, and a new hypothesis was invented that all these supposed entities, these actual, positive existences of some kind of matter called light, heat, etc., really acted through a specific medium, a fluid which pervaded all matter and all space, an invisible, intangible ether, which, once put in motion by the action of light, heat or electricity, had sufficient power to produce all the violent phenomena which were supposed to be the effects of these agents, and this hypothesis is held by many people to-day. Count Rumford disposed of the material theory by immersing two iron or steel bodies in cold water, and then by the friction or attrition of the one upon the other gradually raising the water to the boiling point. This was the initial attempt at removing the consideration of the study of force from the domain of metaphysics to that of physics.

Prof. Grove first publicly announced the modern theory, that the so-called imponderables, light, heat, electricity, etc., are peculiar states of ordinary matter; that they are resolvable into motion, that they are in fact all very closely connected, and the new doctrine was denominated the Correlation of Physical Forces. The doctrine was taken up by others, the real nature of the socalled forces was studied, and the further proposition was enunciated that they are all mutually convertible into one another. It was necessary in the consideration of these forces to study them in their manifestations, to compare them with other physical phenomena, and to note their resemblances or their discrepancies. It has been determined that most, if not all, the forces progress by means

of an undulatory or wave-like motion, not unlike the advance of the concentric waves made by casting a stone into a smooth body of water. This hypothesis is firmly established as regards sound, not only by actual measurement of the vibrations of resonant bodies, but by the very structure of our own auditory apparatus.

The vibrations produced by light have not only been demonstrated, but accurately measured. And not only this, but it is very clearly shown that the different colors of the solar spectrum are produced by a definite number of vibrations upon the retina of the eye. Further, the very number of these wave-like beatings has been ascertained and counted. The most delicate, but at the same time the most determining experiments have been conducted, and these demonstrate that to produce the color at one end of the solar spectrum, red, 480,000,000,000,000 of these vibrations must impinge upon the retina in each second; while to produce violet, the color at the other extreme of the spectrum, the number of vibrations per second is no less than 720,000,000,000,000.

The same arguments which are applicable to the undulatory theory of the progress of light, are equally pertinent in the consideration of electricity, for its mode of progression has been shown to be nearly allied to that of light.

And now, let us for a moment consider the characteristics of some of these forces. Sir Humphry Davy says that the immediate cause of the phenomena of heat is motion, and the laws of its communication are precisely the same as the laws of the communication of motion. We know that all molecular motion is accompanied by the evolution of heat to a greater or less degree. This is equally true whether it be of the changes incited by what is known as chemical action, or the motion induced within the mass of iron upon the blacksmith's anvil. We also know that the same molecular disturbance generates what is known as electricity, and that both these elements are operative in inducing that change sometimes called chemismı. It is equally true that each of these forces is convertible into any of the others. Thus, if we commence with chemical action, we all know how, within the cells of the battery, this action is made manifest in the electrical current, and thus chemical force is converted into electrical force. If now this force be generated in sufficient quantities and conducted along a wire of sufficient size for its easy transportation, and if in this "circuit" a piece of small platinum wire of such size as to partially obstruct the "current be inserted, we all know that the platinum wire soon becomes red-hot, and we

The

see an instance of the conversion of electrical force into heat. galvano-cautery is an illustration of this. If now the current be increased, and the obstruction be entire at one point, the most dazzling radiance is manifest, and here we have an example of the conversion of electricity into light. The electric light is an illustration of this. Here, then, commencing with that simple molecular disturbance within the battery, we see the force generated by those movements manifested first as chemical action; this is converted into electricity, the electricity into heat, and the heat into light, and all without the addition to or the substraction from the original force, as first made manifest, of anything whatever. This proves conclusively that whatever name we may give the phenomena exhibited, they are all due to the same cause, have the same origin, are convertible the one into the other, are in fact all the same thing, differing only in the mode of their manifestation and the accompanying phenomena.

The sun is the great source of light and heat for this earth. The so-called rays of the sun may be made manifest to us in many different ways. If, for instance, we take our stand with that body exposed directly overhead, its influence is chiefly exhibited to us through that which we call heat. But we may interpose between us and the sun crystals of alum, and these will intercept those undulations which are known to us as heat, or in other words, it will so change the character of these vibrations that the sun's influence is no longer manifest to us as heat, but the heat-rays have become light-beams. In other words, the heat is converted into light. Again, we may interpose another substance, and there is neither heat nor light in the sun's influence, but its rays now induce those molecular changes which we know as chemical action. Thus the same rays of the sun may be changed and made manifest to us as light, heat, chemism, or electricity.

Force, then, is but a mode of motion, and according to the manner in which it is manifest to our senses we call it by the names which I have considered. But force may remain latent for an indefinite time. In my school-boy days, when we considered heat, or caloric, we called it either sensible or latent. Further study will teach us that such terms are the result of our lack of understanding of the subject. There may, in one sense, be such a thing as latent force, but heat is only a method of the manifestation of force. The sun is, as I have said, the origin of all force, because within its body certain changes were originally organized and put in motion, whether by Omnipotent power, as our system of theology teaches, or