liker) overlooked it. The history of connective-tissue, and the controversies amongst its investigators, Reichert, Henle, Remak, Virchow, &c., would form subject-matter for many pages of writing. Suffice it here to say that in 1853* Virchow, in writing on the corpora amylacea, described the ependyma ventriculorum as a species of connective-tissue. Further, he pointed out that the central grey matter of the spinal cord (the substantia grisea centralis of Kölliker) is a continuation of this connective-tissue, and that the nerve elements of the central organs are every where permeated and held together by connectivetissue. In 1854, Owsjannikow, in his thesis 'On the Spinal Cord of the Fish,'t demonstrated that both in the anterior and posterior fissure of the spinal cord a process of the pia mater penetrates to the very centre of the cord and surrounds the central canal; and Kupffer,‡ in similar researches on the frog, showed that fibres of connective-tissue are connected with cells of connective-tissue. Finally, Bidder insisted that the grey matter is a matrix for the nerve-cells, consisting of connective-tissue in different stages of development and of numerous bloodvessels. In the white substance, too, there is found a framework of connective-tissue, connected at one margin with the grey substance, on the other with the pia mater. Each white nerve-fibre is encircled by connective-tissue, and in some transverse sections, in which the nervetubes have been dislodged by washing, the skeleton of connective-tissue present in the white substance is beautifully distinct. If the theory of Virchow, that all morbid cell-growths originate in the corpuscles of the connective-tissue, be true, the demonstration of this tissue in every part of the nervous system is pathologically important.

There can, we think, be little doubt that a large part of the grey substance of the spinal cord does consist of connective-tissue, but we do not feel disposed to agree with Bidder and his disciples in believing that all the cells of the posterior cornua are of this character; we should rather regard them (as Clarke, S. van der Kolk and others do) as undoubtedly nervous, whilst those of the smallest size are probably

not so.

In studying the minute structure of this and other parts of the nervous system, the physiologist looks for some plan or type of structure which will harmonize with what experiment has taught him relative to the function of the organ. To us it appears that the time for such a generalization has not yet arrived, and that the many discrepancies amongst observers show the need for much patient inquiry. Nevertheless, some investigators have given such a connected and unhesitating account of their researches, that it is not difficult to lay before the reader a plan of the structure of this complicated organ. The various views entertained on the structure of the spinal cord

Virchow's Archiv, Band. vi.

+ Owsjannikow: Disquis. Microscop. de Med. Spin. Text. in Piscibus. Dorpat, 1854.

Kupffer: De Med. Spinalis Textura in Ranis. Untersuch. über die Textur des Rückenmarkes. 1857. on the Grey Substance of the Spinal Cord. 1859.

Dorpat, 1854. Bidder: Clarke: Further Researches

now presuppose that all nerve-cells give or receive nerve-fibres, and that no such thing as an apolar nerve-cell exists. In a functional point of view, cells may be regarded as— -1st, organs of excitation or stimulation (motor cells); 2nd, as organs through which this excitation is brought into contact with the conscious principle (sensory cells); 3rd, as organs which communicate and modify this irritation in its passage from one fibre to another (reflectory or sympathetic cells). But supposing that cells are functionally distinct, is this difference in their function characterized by any structural peculiarity by which we could recognise them? A Russian observer, Jacubowitsch by name, asserts that they are morphologically distinct, and that in the spinal cord three forms may be distinguished-1st, large multipolar cells which he terms motor cells; 2nd, small cells with three or four processes, which become extremely ramified-sensory cells; 3rd, larger cells than the sensory, round and with only two processes-sympathetic cells. These views require much corroborative observation, and at present can scarcely be accepted on the strength of one observer's opinion.

As regards the course and arrangement of the nervous fibres in the cord very various views are entertained. The simplest and most diagramatic is that of Bidder, and his pupils, Owsjannikow, Kupffer,* &c. These observers believe that the only nerve-cells in the cord are situated in the anterior cornua. These cells are multipolar, and they give off processes which have five distinctive relations-1st, there are processes which connect adjacent cells in the same half of the cord; 2nd, processes which connect together cells of opposite sides of the cord, forming the anterior commissure; 3rd, processes which course upwards to the brain and in the white columns, which are the aggregate of these processes; 4th, processes which go off to form the fibres of the posterior; and 5th, the anterior nerve-roots. According to this view the cells of the spinal cord are structures superimposed on the fibres of the anterior and posterior nerve-fibre in their course to the brain, serving on the one hand to connect the one side of the cord with the other, and on the other to connect anterior with posterior roots with each other and with cells above and below.

Stilling, than whom no one has wrought more at the structure of the cord, takes a view not very different from that of Bidder. He supposes, however, that the posterior cornua contain true nerve-cells which, like the cells in the anterior cornua receive fibres from the corresponding nerve-roots, and send off other fibres to the brain in the white substance of the cord. The cells on the same and on opposite sides are connected in every direction.

In this country important and careful observations have been made by Mr. Lockhart Clarke, but these are of a character much more complex than the observations of most German writers. For a condensed

* Bidder und Kupffer: Untersuch. über die Textur des Rückenmarkes. Leipzig, 1857.

+ B. Stilling: Neue Untersuchungen über den Bau des Rückenmarkes. 1859. Henle und Meissner's Bericht for 1859, p. 198.

account of Mr. Clarke's views, we would refer to a paper published by him in 'Beale's Archiv,' and to a recent paper in the Natural History Review,' in which may be found also an abstract of the latest observations.* Before leaving the subject of, structure, we should like to give the generalization of German observations adopted by Funke in the last edition of his 'Text-book on Physiology.' These

are:

"1. The nerve-fibres, which leave the cord in the anterior roots, take their origin in all animals (as in man) in the ganglionic cells, which are placed throughout the whole length of the cord opposite the points from which the roots go off. No root goes direct to the brain without the interposition of a ganglionic cell. This is the most certain result of all observations on the cord, and few will now dispute it. Even Kölliker, who at first stoutly denied this fact, and held that in the human spinal cord the cells were quite isolated, and had no connexion with the root-fibres, is now inclined to believe in the origin of a part of the fibres of the anterior roots in the cells of the anterior horns. I myself have not only in the frog, but also in the cord of the mammal, distinctly observed processes of the ganglionic cells run deep into the white substance, so that I have no doubt as to the above statement; and especially as no observer has been able to follow an isolated fibre through that cell-group into the white substance of the anterior or lateral columns. When we see

a root fibre coursing amongst these cells without entering them, it is not at all improbable that the fibre terminates in a cell on a higher or lower level. Still less may one assume with Lenhossék, when we see a fibre apparently end free between the cells, that a free ending occurs in that spot, but must rather suppose that what appears to be the end of a fibre is merely a section of one as it is bending upwards.

"2. All the fibres of the anterior roots stand in mediate connexion with the brain, through the processes issuing from their ganglionic cells into the white substance. As a rule, a great number of root-fibres appear to end in a group of anastomosing cells, from which only one or two channels of communication go off to the brain. The existence of anastomosing systems of nerve-cells in the anterior horns, is, in my opinion, an undoubted fact not only in man and mammals, but also in the cord of the lower vertebrata, as I have convinced myself, contrary to the opinion of Kupffer and Owsjannikow. I have isolated cells from the anterior grey substance of the frog with more processes than the Dorpat school have described, in which some of the processes, more espe cially those which run inwards and backwards, divided in a fork-like manner. I have also most distinctly seen in the frog that the cells were connected with each other. How it happens that such a master of observation as Kölliker has observed no undoubted cell-anastomosis is an enigma. It remains to be proved whether the processes of these anterior cells ever end free.

"3. There is no crossing of the anterior root-fibres in the cord, but a mediate connexion of the anterior roots of both halves of the cord takes place through the anterior grey commissure, which is nothing else but the connecting fibres of the cells of both sides. What Kölliker has taken for a crossing of the anterior columns, and what others hold to be an anterior white commissure, is nothing else than the crossing of the connective-tissue fibres of the pia mater in the substance of the cord, which was first discovered by Arnold, correctedly described by Blattmann, aud particularly so by Kupffer. We shall see that physiological experiment is also opposed to the idea of the crossing of the anterior roots. After several careful examinations of fresh and hardened preparations of the cord of the frog, I have been unable to

*Goll, Trask, Reissner, Stieder, Dean, Traugott,

convince myself of the nervous nature of the system of cross fibres behind the anterior fissures.

"4. In regard to the relations of the posterior roots, we have less sure data. Bidder and his pupils hold that in a frog and in a fish all the posterior roots enter the ganglionic cells, from which the anterior roots spring. From my own studies in the subject I am convinced that this is the case with a part of the fibres, but not with all. Certainly, in the higher animals, in which the greater part of the posterior roots does not enter the ganglionic cells, Bidder's idea does not hold. Whether these fibres pass through ganglionic cells in the grey substance, before they pass over into the central channel of the white substance, and whether a crossing takes place behind the central canal, are still undecided questions. Schröder van der Kolk has lately convinced himself of the ending of the sensitive root-fibres in ganglionic cells of the posterior horn, and supposes that the farther conduction of impressions proceeds to the other side, and in this to the brain. He bases this supposition also on the analogy of the sensitive nerves which terminate in the grey nuclei of the medulla oblongata. The existence of a posterior grey commissure, and its importance as a cross-passage of the posterior nerve-roots, I hold as very probable; and I believe it occurs even in the frog, as Kölliker and others have lately testified. From a physiological point of view, the existence of fibres which go to the ganglionic cells of the anterior roots as the direct passage of the greater part of the posterior root-fibres in their passage to the brain, and, finally, decussation of the posterior root-fibres, may be supposed. A direct transition of the posterior root-fibres into the anterior I hold as improbable.

"5. The longitudinal fibres of the white substance come collectively out of the grey substance, and represent mediate or immediate continuations of the anterior and posterior root-fibres. All processes of the first rise from the ganglionic cells of the anterior grey substance in which the anterior root-fibres originate. How far the continuations of the posterior nerve root-fibres communicate directly, or through the medium of cells, with these fibres, is yet to be ascertained.

"6. The grey substance consists of a stroma for ganglionic cells, in which these connect themselves with root-fibres or with each other. It is doubtful whether in the grey substance nerve-fibres exist which are not related to its ganglionic cells."

In connexion with the structure of the spinal cord, we would refer to a very interesting paper by Dr. T. S. Clouston on the Minute Anatomy and Physiology of the Nervous System in the Lobster.' In this animal it is found that, in every essential point, the ganglia and interganglionic cord correspond to the spinal cord of the vertebrate animal. The origin of fibres from cells, the connexion of cells with each other, a connexion between the various groups of cells in different ganglia, and a correspondence between the number of ganglionic cells and that of the muscles which they minister to, are facts (Dr. Clouston shows) equally susceptible of confirmation in the invertebrate as in the vertebrate class of animals.

In analysing recent observations on the function of the spinal cord, it will be convenient to regard the organ in a three-fold character : 1st, as a centre for the reflection of impressions made on its afferent nerves; 2nd, as a sensorial centre; 3rd, as a conducting organ.

I. The spinal cord is a reflecting centre-i.e., an organ capable of converting impressions made on its afferent nerves into motor impulses, without and independent of the co-operation of the will.

of the earliest to perceive this fact was Prochaska, but it was left for our distinguished countryman, Marshall Hall, to indicate the importance and to explain the conditions of the reflex endowments of the spinal cord. Since his time (1833-43) the subject has been specially considered by Müller (1834); Volkmann (1838); Valentin (1839); Arnold (1842); Grainger (1837); Spiess (1844); Weber, Wagner (1854); and last, but not least, by Edward Pflüger (1853).

The study of reflex action can be conducted only under circumstances in which the influence of the will is excluded. Accepting the conclusion that the brain is the exclusive organ of the psychical functions; that in it only occurs perception of sensitive impressions (sensation); that from it alone proceeds the influence of the will, it would follow that all the motions produced in a decapitated animal were of a reflex character. But this conclusion has not only been doubted, but strenuously denied; and in the modern text-books of physiology we meet with the query, "Sensorium im Rückenmark?" A little consideration of this question may interest the reader.

In 1853, Pflüger published a work* in which it was contended, from experiments on animals, that the spinal cord is the seat of sensorial functions. In earlier times this idea was hinted at, and even distinctly indicated, by Prochaska, Legallois, Cuvier, and Volkmann. One of Pflüger's most striking experiments is the following a frog is decapitated, and acetic acid is placed just over the internal condyle of the femur. The animal constantly bends the limb, and with the dorsal surface of the foot of the same side wipes off the acid by alternate movements of ad- and ab-duction. This we have often seen. The foot is now cut off, so that " wiping" is no longer possible, and the acid is reapplied. The animal bends the thigh as formerly (for it still supposes it possesses its foot), but it soon gives up this movement, becomes restless "as it seeks after a new method," and finally using the limb of the other side, bends it, so that by the sole of the foot the acid is removed. If other modes of irritation are employed, the movements which follow are said always to present an appearance of purposiveness (Zweckmässig keit).*

But mere purposiveness of action would not prove the existence of psychical activity in the cord, for are not all reflex arrangements purposive in their object? We must look to some other characteristic. Supposing that each sensitive fibre is connected mediately with a system of motor fibres, so that the former may, when excited, call forth a determined harmonious muscular action (such as the will would call forth), then we must expect that the action called forth by the excitation of a centripetal fibre must always be the same when the exciting agent is similar, and applied under the same conditionsin fact, with such a mechanical arrangement as we have supposed, we would expect a degree of regularity in the results of au excitation. It is urged by those who contend for the sensorial functions of the cord,t

* Die sensorische function des Rückenmarkes der Wirbelthiere nebst einer neuen Lehre über die Leitungsgesetze der Reflexionen. Berlin, 1853.

+ Pfluger, Funke, Auerbach.