the conclusion is inevitable that the conduction of nerve force does not take place by means of fibres only. The fibres may be special organs of conduction, and as special organs a corresponding specialty of function must be assigned to them; and into this we shall now inquire. Let us assume that the homogeneous nerve transmits the impression in a mass, just as the sounding-board of a piano, if struck, will yield a certain resonance; but the fibrous nerve will transmit the impression along each separate fibre, just as the soundingboard when struck by keys; the amount of nervous impression and the amount of sound in each case may be equal, but the varieties and combinations possible to the latter are impossible to the former. Or to vary the illustration, let us assume two men to be equally susceptible to the general effect of colour, but one of them, an artist, to have more susceptibility to the minute differences of colour;--although the nervous impression may be equal in the two, it will be less homogeneous in the artist, whom we may suppose to have a more specialised retina. The assumption that fibres are organs of conduction at all, may be disputed; nor, if what was previously said respecting the identity of cell and fibre, in ultimate structure, and of the identity of ganglion and tube, be admitted, can we allow the old hypothesis of conduction to be more than a metaphor. The notion of an actual conduction taking place, analogous to the conduction of electricity, is extremely doubtful to me. If the nerves are identical in elementary structure with the ganglia, and consequently must participate in the functions of the ganglia, they can no longer be regarded as the conducting rods of the battery, but as essential parts of it. In our present ignorance of the true process we may continue to employ the metaphor of conduction, if we understand by it simply the change which follows when a nerve is affected; and we may then gain some glimmering of the special function of the fibres, and the meaning of their increase with old age. Nerve-tissue in its earliest stage is wholly without fibres; as development advances, the fibres multiply.* In old age the brain hardens from excess of fibres, as the bones harden from excess of lime; so that what originally constituted a source of strength becomes a source of weakness. Probably to this predominance of fibres may be assigned the incapacity of acquiring new ideas in old age. Intellectual vigour is often manifested by men of a very advanced age, but the vigour is shown in dealing with old trains of thought, not in originating new. To assume a new attitude of thought, it may be necessary to develop new fibres; and this cannot be done in a tissue already too fibrous. A similar hypothetical explanation suggests itself for the formation of fixed ideas, monomanias, habits, and tendencies" organised tendencies," as Mr Herbert Spencer felicitously names them.t But I will not venture further into this hypothetical region; the few anatomical facts hitherto ascertained presenting too narrow a basis for such speculations. One embryological indication may, however, be added. The nerves of insects are, it is known, distinctly fibrous (although in the bee and locust I have observed the fibres occasionally melting into mere granules), but in the larvæ of insects the nerves are often mostly granular. Thus in the active predatory Dragonfly Larva- the watertiger, as it is called-I found the great ventral chord formed of distinct fibres, but in many places it was purely granular, the granules not having even a linear disposition. In the have stated would surprise me-for instance, that fibres could be found in a Doris, a Pleurobranchus, an Aplysia, or a Solen-I meant to be understood that such exceptions would in nowise invalidate my conclusions, for which, indeed, one single case of non-fibrillated nerve would be ample evidence. Not till the beginning of the fourth month of the human embryo are fibres discoverable in the spinal chord.-TIEDEMANN, Anatomie du Cerveau, p. 126. HERBERT SPENCER, Principles of Psychology, 1855. In more advanced Larvæ these chords are wholly fibrous. preparation I have made of this object a very interesting analogy between the development of nerve and muscle is presented. A fragment of muscle is attached, the fibrille of which, instead of being striped (all the muscles of insects are of the striped kind), are partly striped, partly unstriped; that is to say, in the same bundle some of the fibrille are with out the transverse markings, and those fibrilla which have such markings have them only part of the way down, the remainder of the fibrille being unstriped. This is not only interesting as a fact of muscular development, but presents a striking analogy to the development of nervefibres, which we here see in the same trunk partly emerged from their primitive granular condition. I conclude, therefore, that the differentiation of nerves shows the following phases: 1°, as in many molluscs and all embryos, a granular homogeneous mass; 2°, as in insects, and perhaps crustaceans, a linear disposition of the granules into fibres, but without an investing sheath; 3° fibres, or rather tubules, differing from the preceding, in having each an enveloping sheath, which isolates one fibre from the other, so that the nerve becomes a fasciculus of tubules.* It would lead us too far to follow the many applications of these facts to the vexed questions of nervous histology and physiology. The hotlydebated controversy respecting the origin of fibres as prolongations from ganglionic cells, for example, seems to me decisively settled by the fact that, in the molluscs, we have cells without fibres, and by the fact that, in the recently-born dog, we have fibres which have not yet effected a junction with the cells. Again, when Funke, reviewing the controversy respecting the existence of ganglionic cells destitute of processes, says that, "from all we know of the functions of the nerve-elements and the laws of conduction in them, an isolated apolar nerve-cell appears as an anomaly (Unding) to which we can in nowise assign a physiological purpose," + he is assuming that without fibres terminating in cells no nervous transmission can take place -an assumption flatly contradicted by the facts we have just been considering. Hitherto our remarks have been of a revolutionary tendency. To unsettle established opinions, to shake the very foundations of nervous physiology, and to show that we are in no condition to propound theories, otherwise than as provisional attempts, has been the serious business of this article. Brown-Séquard has proved that the doctrine of the schools relative to transmission by the spinal column is in every point erroneous. Stilling has proved that the dissident doctrines of the schools respecting the ultimate structure of nerveelements are erroneous or incomplete. And I have proved that the doctrine of the schools relative to the function of the fibres is erroneous-that conduction does not necessarily imply the existence of a continuous fibre from the periphery to the cell, and from the cell again to the periphery; but takes place where there are no fibres at all, and where a solution of continuity exists. Nor is this all. What we metaphorically call "nervous conduction" takes place not only in the absence of fibres, but also in the absence of any nerves whatever. There is nothing like the sharp angle of a paradox to prick the reader's attention; and here is one in all seriousness presented to him. The fact is demonstrable, that both Contractility and Sensibility are manifested by animals totally destitute of either muscles or nerves. Some physiologists, indeed, misled by the a priori tendency to construct the organism in lieu of observing it, speak of the muscles and nerves of the simplest animals; because, when they see the phenomena of contractility and sensibility, they are unable to dispossess themselves of the idea that these must be due to muscles and nerves. Thus, when the STILLING, op. cit. p. 11-13, decides that all primitive fibres have an investing sheath; but unless he would deny the claim of those named in the second class to be considered as fibres, he is certainly wrong. +FUNKE, Physiologie, p. 419. fresh-water Polype is seen capturing, struggling with, and finally swallowing a worm, yet refusing to swallow a bit of thread, we cannot deny that it manifests both sensibility and contractility, unless we deny these properties to all other animals. Nevertheless, the highest powers of the best microscope fail to detect the slightest trace of either muscle or nerve in the Polype. To call the contractile substance a "muscle," is to outrage language more than if a wheelbarrow were spoken of as a railway locomotive; and as to nerve substance, nothing resembling it is discernible. In presence of these facts, those who cannot conceive Sensibility without a nervous system, but are forced to confess that such a system is undiscoverable, assume that it exists" in a diffused state." I have noticed this illogical position in a former paper. It is a flat contradiction in terms: a diffused nerve is tantamount to a liquid crystal; the nerve being as specific in its structure, and in the properties belonging to that structure, as a crystal is. Now, this specific structure-or anything ap proaching it is not to be found in the Polype.* Whence, then, is the Sensibility derived? Either we must admit the presence of what cannot be discover ed; or we must admit that a function can act without its organ; or, finally, we must modify our conception of the relation between Sensibility and the Nervous system. Which of these three conclusions shall we adopt? Not the first; for, to admit the presence of an organ which cannot be discovered, even by the very highest powers, although easily discoverable in other animals by quite medium powers, would be permissible only as the last resource of hypothesis, when no other supposition could be tenable. Not the second: for philosophic Biology rejects the idea of a function being independent of its organ, since a function is the activity of an organ. The organ is the agent, the function the act-a point to which we will presently recur. The third conclusion, therefore, seems inevitable: we must modify our views. But how? Instead of saying, “Sensibility is a property of nervous tissue," we must say, "Sensibility is a general property of the vital organism which becomes specialised in the nervous tissue in proportion asthe organism itself becomes specialised." We have no difficulty in understanding how Contractility, at first the property of the whole of the simple organism, becomes specialised in muscular tissue. We have no difficulty in understanding how Respiration, at first effected by the whole surface of the simple organism, becomes specialised in a particular part of that surface (gills or lungs) in the more complex organisms; nor should we have more difficulty in understanding how Sensibility, from being common to the whole organism, is handed over to a special structure, which then performs that function exclusively, as the lungs perform that of respiration, or the muscles that of contraction. Nay, more: just as animals possessing special organs for Respiration do also, in a minor degree, respire by the general surface, so, according to my observations, it is almost demonstrable that animals possessing a special nervous system also manifest sensibility in parts far removed from any nervous filament. In the higher animals this is probably not the case.† The division of labour is more com * "Sarebbe una vera perdita di tempo," says DELLE CHIAJE, "per colui, che volesse ricercare nervi negli animali Infusori nei Polipi, nelle Meduse e nelle Actinie."Istituzioni di Anat. e Fisiolog. Comparata, i. 118. He denies the existence of nerves even in the Holothuria. So likewise does VOGT, Zoologische Briefe, with several other anatomists. + I say probably, because recent investigations have shown that parts which, in the normal healthy condition, are absolutely insensible, such as tendons, ligaments, the dura mater, and the periosteum, become intensely sensitive in a state of inflam mation, and this cannot be attributed to the nerves.-See FLOURENS, in Annales des Science Naturelle, 1856, IV. Série; vi. 282. Further, Mr ToMES has communicated to the Royal Society a paper on the "Soft Fibrils in the Dentinal Tubes," which shows a sensitive structure, not nervous, in the teeth. plete. The stomach digests, the glands secrete, the muscles contract, and the nerves feel. Of course, the power is greatly increased by this division of labour; the more complex the organism, the more various and effective each function. It is truly remarkable that the zoologist who claims the merit of having originated this conception of the "division of labour" as a law in the organic economy, should be among the stanchest defenders of the old metaphysical idea that functions are not dependent on organs; and as this question is not only important in itself, but of interest in the present discussion, it may detain us for a moment. The argument, as conducted by Milne Edwards,+ is irresistible, because in it he confines himself to showing that special organs may disappear, and nevertheless the general function remain; for instance, that lungs and gills may be absent, but the function of Respiration will still be present: "C'est une erreur grave de croire," he says, qu'une faculté determinée ne puisse s'exercer qu'à l'aide d'un seul et même organe." The grave error appears to me wholly on the side of those who hold the contrary opinion. The reader will perceive that when Milne Edwards concludes, que la fonction ne disparait pas lorsque l'instrument spécial cesse d'exister," the eminent zoologist is guilty of a logical mistake very frequent in biological discussions, the mistake of confounding the general with the particular. Thus an animal may possess the general function of Locomotion, without possessing the special function of walking or flying; it may have the general function of Sensibility, without the special Senses; the general function of Assimilation, without special Digestion; for the special functions special organs are required, legs or wings, eyes or ears, intestinal canal, and so forth. The peculiar faculty of locomotion known as "flying," can only be performed by the peculiar organs known as "wings;" but the general faculty of locomotion can be performed by a simple contractile tissue. As soon as we disengage language of its ambiguity, the truth is easily seen the appearance of each special organ in the animal series is coincident with the appearance of a special and corresponding function; or, descending the scale, with the disappearance of each special organ, the corresponding specialty of function disappears. In other words, Function is dependent on Organ, as the Act is on the Agent. Would it not seem wholly preposterous to say that railway locomotion was not necessarily dependent on railways, because, before railways were invented, goods and passengers were transmitted by waggons and coaches? Does not every one see that the special form of railway transmission gives it a power, velocity, and extent, wholly unattainable by waggons and coaches; and that this power, velocity, and extent, are due entirely to the peculiarity of the methods of transit? The railway differs from the tramway, and the tramway from the old coach-road, in special modifications, as the lungs of a mammal differ from the gills of a fish, and the gills from a merely respiratory surface in the Zoophyte. To say that the same function is performed by all, is to confound the general with the particular; and to say that functions are consequently independent of organs, is worse than this, because it leaves out of sight the fact that the whole surface of the animal which respires is the organ" of that general respiration. When acts can be performed without agents, and animals can exist without bodies, in the shape of pure syntheses of functions, then will it be a "grave error" to conclude that functions are * MILNE EDWARDS. See his Introduction à la Zoologie Générale. The conception, however, belongs to GOETHE; Zur Morphologie, 1807; Werke, xxxv. i. 7—the French naturalist having the merit of application and abundant illustration of the law. + Loc. cit. p. 69, and Leçons sur la Physiologie et l'Anatomie Comparée, i. 22. "Les faits dont je viens vous entretenir montrent combien sont fausses les opinions de quelques naturalistes qui admettent comme une sorte d'axiome physiologique que la fonction depend toujours de son organe." necessarily dependent on organs, and not till then. Although we have been forced to admit that Sensibility can be manifested without nerves, and the paradox therefore of nervous conduction taking place without nerves was only a paradox in its terms, yet inasmuch as functions are necessarily dependent on organs, we are also forced to conclude that the various specialisations of nerve-tissue must bring with them corresponding specialisations of function. What those are we know not, perhaps may never know; but the mere recognition that such things must be, will help us to understand many points. It explains, for example, the absence of Pain in the lower animals, spoken of in our last; it explains the possibility of such myriads of subtle differences in the perceptions of men so nearly allied as twin-brothers. Such questions prove, dear reader, how naturally we are led by Sea-side Studies into the solemn temples of Philosophy. Indeed, it is one of the many charms of such a study, that at all points it is connected with Art, Science, and Philosophy. The naturalist may be anything, everything. He may yield to the charm of simple observation; he may study the habits and habitats of animals, and moralise on their ways; he may use them as starting-points of laborious research; he may carry his newly-observed facts into the highest region of speculation; and whether roaming amid the lovely nooks of Nature in quest of varied specimens, or fleeting the quiet hour in observation of his pets-whether he make Natural History an amusement, or both amusement and serious workit will always offer him exquisite delight. From the schoolboy to the philosopher, all grades find in it something admirably suited to their minds. It brings us into closer presence of the great mysteries of life and while quickening our sense of the infinite marvels which surround the simplest object, teaches us many and pregnant lessons which may help us through our daily needs. "And of such truths MODERN LIGHT LITERATURE-SOCIETY. LITERATURE is under limitations; it is like every other faculty of the human mind, unable to express half of what it would express, or make other people aware of a tithe of what it knows in common with other people. Poetry, it is usual to say, comes to our heart, because it expresses what we all feel, but what only one of us, here and there, has the gift to say. Yet even the greatest poet touches upon the great ocean of secret individual experience and sentiment with the timid hand of a schoolboy; puts one thought at a time into minds which throb and burn with a hundred simultaneous thinkings, and to his own consciousness is dumb and voiceless, unable to say more than very morsels and fragments of what is in him. We believe there never was story made of the most intense emotion, but its humblest reader could have turned aside to think of a truer, intenser, deeper depth in his own uncommunicating heart; and perhaps it is for this reason that a full picture of life, as it is, is never possible to us. We have bits of life in plenty scenes external-interiors such as one can peep at through a lighted window; private self-revelations, in which it is still very easy to see that the self is not half revealed; but life, such as we live, to its full extent, and in its veritable details, never. What man, worth the name, would tell his own history pang by pang, and thought by thought? Who would venture to leave the world a picture -or who could, even if he ventured -of all the undistinguishable ghosts that throng his mind and fancy every hour of every day? Nobody thinks-save in a business fashion, when it happens to be one's trade, and when one's thoughts are technical, professional, bent to a purpose; but everybody is possessed with |