4. Transactions of the Cleveland Literary and Philosophical Society-Science Section. Vol. I., 1868-69.

5. "On Our Foreign Competitors in the Iron Trade:" A Paper read to the North of England Ironmasters, by I. Lowthian Bell. 29th September, 1868.

6. "The Chemistry of the Blast Furnace:" A Lecture delivered to the Chemical Society of London, by I. Lowthian Bell.

1869.

7. Transactions of the Iron and Steel Institute. Session 1869. 8. The Industries of the Tyne, Wear, and Tees. 2nd edition. Longmans.

DESCRIPTION OF THE XYLOGRAPHIC PLATES.*

I.-FIRST AGE OF IRON-MAKING.-A pen-and-ink sketch, made by Captain Grant, who accompanied Speke to Lake Nyanza. It represents native Africans making malleable iron direct from the ore. The ore is placed in the low charcoal fire, and a man on each side urges it by means of bellows (two single-acting-that is, four single-acting in all), so as to keep up a continuous blast.

II. SECOND AGE OF IRON-MAKING.-Illustrated by the blast furnace at Mariedam, in Sweden, where the low hearth has passed through the intermediate stage of the blanofen, and arrived at the high or true blast furnace for the manufacture of pig-iron. Height, about 40 feet; built of rough stones bound together by logs of timber painted red; using charcoal, and making from thirty to forty tons per week during four or five months in the year.

III.-THIRD OR CLEVELAND AGE OF IRON-MAKING. - Illustrated by the Wear Furnace at Washington, co. Durham. This furnace makes about 330 to 350 tons of iron per week from coke made on the spot, the heat from the coke ovens being used for heating the blast. The furnace gases are also partially used for this purpose, for raising steam for the blast engine, and for boiling down certain solutions in the adjoining chemical works. The exhaust steam from the engines heats up a large quantity of water required in the chemical works. The ore smelted is the Cleveland stone, with a small quantity of residual oxide of iron from the chemical works, nothing being wasted.

IV. DEATH OF AN IRONWORKS.-This sketch represents two furnaces, built on a landslip, on the Yorkshire coast. After the works were finished, the land slipped a little further, and reduced the place to a ruin within two months. The owners, nothing daunted, rebuilt the works, and a second ruin resulted from the total absence of ordinary judgment shown in building on such a site.

* The photographs for these plates have been kindly contributed by I. Lowthian Bell, Esq.

IV. ON "TROPHIC NERVES."

By GEORGE ROLLESTON, M.D., F.R.S., Linacre Professor of Anatomy and Physiology, Oxford.

ALL physiologists, and indeed all observers, whether physiologists or not, are agreed that the nervous system intervenes most powerfully, and that not rarely, in controlling and modifying the processes of what we call "organic life." Growth and development, it is true, may be carried on, food may be assimilated, and secretions may be elaborated, independently of nerves and nerve-centres in many lower animals; but, on the other hand, it is equally true that in more highly organized creatures there are but few processes of vegetable life which may not be, at times and to a greater or less degree, brought under the influence of their cerebro-spinal systems. As to the facts, there is no question; as to the way in which the facts are brought about, however, there is a very wide difference of opinion. This difference is expressed in the contradictory answers given by representatives of various biological schools to such questions as-Can the nerves act directly upon cells other than muscular fibre cells? Can nerve-force interfere with the cell territory otherwise than by regulating the stream of nutriment brought within the borders of that territory by the blood-vessels? Are there, finally, "trophic" and secretory as well as vasomotor nerves? The indirect action of nerves upon tissues in the way of vasomotor regulation of the blood-vessels supplying them is more readily comprehensible by us, but that nerves can act directly upon cells pigmentary, secretory, and other cells, as well as upon contractile cells and fibres, appears to the present writer all but equally demonstrable. Change of colour in ourselves is usually dependent upon vasomotor change; but change of colour in the frog has been most conclusively shown by Professor Lister to be dependent upon molecular movements carried on in the interior of cells under the influence of the nervous, and under circumstances which exclude the intervention of the bloodvascular system. A force which can be seen to produce molecular movement within a pigment cell, may well be supposed to be competent to produce nutritional or chemical changes in the interior of cells of other characters. But if our knowledge of the convertibility of force makes us ready to allow that nerve-force may show itself by modifying nutrition or by producing secretion as well as by producing motion, our knowledge of the convertibility of function which nerves possess accordingly as they are distributed in one or in another class of tissues makes us slow to accept as a necessity the establishment of a division of "trophic" nerves. Messrs. G. H. Lewes, Philippeaux, and Vulpian have shown that nerves are sensory

or motor accordingly as they are distributed to sensory or contractile tissue-elements, and not by virtue of any inherent differences in their own structure; and if we have thus to modify our views, if not as to the use of the words sensory and motor nerves, at all events as to the meanings we attach to them, it would be doubly inexpedient to introduce now new words, "trophic" and secretory; considering, firstly, that they are not old and familiar to us, nor possessed therefore of a claim upon our toleration; and, secondly, that they labour under just the same disadvantage of needing to be used with a mental qualification as the older words in question. This is, however, but a question of words; and it may be well now first to state the facts so far as they appear to have been ascertained by observation and experiment; and then, in the second place, to suggest, or leave the reader to excogitate for himself, such a reading of them as may seem best fitted to bind them together into a bundle easy to be manipulated by the mental hand.

I will begin by giving a few facts which bear directly enough upon the influence exercised by psychical changes and cerebral affections upon processes of vegetative life, but which do not give any clear indication as to the way, whether vasomotor or intracellular, in which that influence is brought directly to bear. Facts of what some persons would call great generality, but what others would, and with greater propriety, call great complexity, are presented to us in the familiar histories of defeated armies and of other bodies of men subjected to depressing psychical influences. Such aggregations of men are found to be more liable to succumb to various unhealthy influences, such as those of dysentery, scorbutus, and malaria, than are other aggregations of men similarly constituted except as to their mental impressions or depression. But in generalibus latet error; and as we have exact quantitative observations, showing that prisoners in civil gaols perform the ordinary functions of life less perfectly, and at greater cost to their own organism, as also to that of the body politic, than do honest, or, to use the safer term suggested to me by a warder in Portland prison, unconvicted men, we had better refer to them. These observations will be found recorded in the Report of the British Association Meeting held in Manchester in the year 1861, at p. 59, and, passim, in a "Report on the Action of Prison Diet and Discipline on the Bodily Functions of Prisoners," which we owe to Dr. Edward Smith, F.R.S., and Mr. W. R. Milner. The "cerebral exhaustion," again, so common in these days of stress and tension, is well known (as well it may be, considering what abundant opportunities we have for observing it) to exercise a similarly "atrophic" influence. Modern language, indeed, by altering the meaning of the word indolence from that of freedom from pain to that of freedom from labour, appears to show us that the real relation of overwork to disease has been more or less obscurely

recognized by the laity, even at times when the faculty inverted the relations of effect and cause which really do exist between many manifestations of mal-nutrition, such as dyspepsia and cystitis, on the one side, and cerebral overwork and spinal exhaustion on the other. It is to Dr. Gull* that we owe a demonstration of the facts that the painful affections specified, as well as others only alluded to, are antecedents, but in the sense in which a man's shadow antecedes him when the sun is at his back; that the doctrine of reflex paraplegia was wrongly applied to those cases; and that they are really to be explained as being of the same character as those furnished to us in the histories of men subjected, in prison, as if in an experiment, to the working of mental depression.

Simpler cases still are furnished to us by the well-authenticated accounts of persons losing all their hair after cerebral injury.t When we consider how large an organ the brain is relatively to the rest of the body, and how, protected as it is by its lodgment within an air-tight cavity, it can say to all other organs of the body, "Thou shalt want before I shall," there is no need to waste time in imagining how its derangement may and must entail derangement throughout the entire body. It may be profitable to discover by investigation how this secondary derangement is brought about, whether indirectly by vasomotor alteration, or directly by molecular disturbance set up intracellularly. At present the necessary investigations have not been set on foot; and, ad interim, we may colligate the facts under Mr. Darwin's expression of "correlation of growth."

We come in the third place to cases of greater simplicity still; and by this we do appear at first sight to be brought within the sphere of the explanation which the phrase "Trophic nerves" implies. These cases are constituted by the accidental severances of nerves which take place in civil, and more especially in military life, the musculo-spiral nerve, whence the greater part of the thumb and lesser proportions of the three fingers next to it receive their dorsal supply, being specially well fitted for such experimentation, and specially obnoxious to it in the "pious pastime" of war. Dr. S. Weir Mitchell has put on record, in The Contributions relating to the Causation and Prevention of Disease, and to Camp Diseases,' edited by Dr. Austin Flint, and published by the United States' Sanitary Commission, some very valuable observations as to the effects of such injuries to nerves. These we find summed up as follows by a writer in the Edinburgh Monthly Medical Journal' for January, 1869, at pp. 646, 647:

"There is a careful and interesting description of glossy skin *See 'Guy's Hospital Reports,' iii., 7: 1861.

+ See Lancet,' July 10, 1869; and 'Holmes' System of Surgery,' i., article "Accidents from Lightning," p. 750.