devoting time and thought to the matter, which may even enable us to multiply many fold the amount of light which we can obtain from a given quantity of energy. There is yet another direction in which possible economy is to be looked for, a very fascinating one, and by no means an unpromising one. Look for a moment again at Fig. 5. Except only the process at the lamp itself, all the transformations have fair economy, so good that one sees at once that no radical defect exists in them. But cannot some of these be done away with altogether? It is the number of them that tells, and brings down the final result. If an ordinary gas engine be substituted for a steam engine we cut out one transformation altogether. The boiler losses disappear, or rather, such corresponding losses as exist occur in the gasworks. At the same time we substitute the higher efficiency of the gas engine for the lower of the steam engine, which may be a very important matter. It is practically equivalent to cutting G out altogether. Of another kind is the possibility at present much talked of, the substitution namely, not only of a gas engine for a steam engine, but at the same time also of a gas producer for a boiler, so that the motor fluid should be producer gas made on the premises and not steam or coal gas from public mains. There seems no doubt that the combination, although it does not much reduce the number of transformations, gives under certain conditions a very high economy of fuel indeed. I do not think the evidence before us is as yet sufficient, although I hope it shortly will be, to enable us to say how far under ordinary working conditions the actual combined efficiency of the whole plant will be distinctly greater than that of existing systems. [The lecturer dealt with the question of the utilisation of dustbin refuse, of the economic efficiency of electric tramways and of compressed air transmission, illustrating these by diagrams. He discussed also the effect of "load factor" on economic problems. He then concluded as follows:-] To sum up the whole matter in the way of possibilities and impossibilities, there does not seem to be anything very startling before us in the way of possible economies, except in the two directions of efficiency of lamps as light producers, and of bringing up gas engines to their theoretical maximum. In other respects matters are running along lines which I have endeavoured to indicate, and along which they will doubtless develop more or less rapidly, but always less and less rapidly as they get nearer their limiting efficiency. There is no one point in which we have not some measurements which enable us to set bounds to the possibility of improvement along any known lines, and thus we have means for gauging the value of the pretensions made by each new method, or scheme, or invention, as it appears not merely guessing at it, but actually estimating its possible value numerically. For those of us who are not born to be inventive geniuses there is always the consoling thought that the difference between good engineering and bad engineering in economy, with the very same materials, is very much greater than the difference between good engineering and any probable improvements upon it. And meantime, we find our hands sufficiently full in trying to keep up to the best existing standards, pending the time when Messieurs the discoverers show us how to get on a little further. [A. B. W. K.] WEEKLY EVENING MEETING, Friday, April 28, 1893. SIR JAMES CRICHTON-BROWNE, M.D. LL.D. F.R.S. Treasurer and Vice-President, in the Chair. FRANCIS GOTCH, Esq. M.A. F.R.S. The Transmission of a Nervous Impulse. THE lecturer opened with a short account of the present state of our knowledge as to the anatomical structures of nerve-fibres. He then described and repeated the experiments of Helmholtz, made 50 years ago, with the object of ascertaining the rate at which a nervous impulse was conducted along a nerve-fibre. These experiments form the basis of our more exact knowledge as to that capacity for transmission which is the peculiar vital function of nerves. The essential feature in the process is the power which each individual part of the living nerve-fibre possesses of awakening in response to a sudden change in its physical environment, this property being expressed by the term "excitability"; in the transmission of the nervous impulse each successive individual part awakens in consequence of the subtle changes present in its aroused neighbours. The awakening thus travels along the nerve as a flame along a fuse. The power of transmitting a change, and the power of initiating such change in response to a stimulus, in other words, conduction and excitability, are thus brought into correlation. The lecturer then proceeded to demonstrate and describe experiments carried out by Mr. J. S. Macdonald and himself, in the Physiological Laboratory of University College, Liverpool, upon this subject, these experiments having been made in order to ascertain how far these two properties, (a) of responding to an external stimulus, (b) of transmitting the nerve impulse started by such a stimulus, could be considered as identical. In order to ascertain this, an agent was used to modify, on the one hand, the capacity of the nerve to be aroused by physical agencies, and on the other, its power of transmitting an impulse when aroused. The agent employed was a localised alteration in temperature, and experiments were described and demonstrated which showed that whereas cooling to 5° C. tended to block the transmission, such cooling, far from rendering the nerve less responsive to external stimuli, made it more readily affected by the stimulating influence of a large number of physical agencies. Such agencies were shown to be (1) galvanic currents, (2) condenser discharges, (3) mechanical blows, (4) chemical reagents. To all these the nerve responded better when cooled, though it transmitted the nerve impulse produced by such response with greater difficulty. To one agent only did the nerve respond less readily when under the influence of localised cold; this was the induced electrical current. It thus appears necessary to reconstruct our view of the nature of the process during nerve transmission, for the two events in the nerve, the response to external stimuli and the power to transmit such response, are affected in a diametrically opposed manner by such a simple change as alteration in the nerve's temperature. The favourable influence of localised cold on the response of excitable tissues to external stimulation was further displayed by description and demonstration of the effects produced when muscles, and not nerves, were the objects of experiment. In all cases cold favoured the capacity of the muscle to reply to the stimulus. Finally, the lecturer brought forward some observations which appeared to show that in addition the transmitting power of a nerve is largely affected by the nature of the agent which started the nerve impulse. We have found it possible to arouse a nerve by a galvanic current in two ways: (1) so that localised cooling of a portion of the conducting path will favour the passage of the impulse (the normal condition), and (2) so that the same localised cooling will block the impulse. It would thus seem that nervous impulses, when started on their journey along nerves, bear throughout that journey some impress of the agent which started them, and hence, that the impulses which are initiated by even slightly different physical agencies, and are then transmitted along nerve-fibres, differ from one another as regards the character of some fundamental quality. Professor Gotch concluded that these and other recent observations gave experimental proof that the property of transmission possessed by nerves is correlated, not merely with that of excitability, but largely with the source, and thus the nature of the impulse, so that the unknown molecular changes which form the living basis of such transmission in any one nerve-fibre are not the same for all impulses, but change with the source of each. [F. G.] ANNUAL MEETING, Monday, May 1, 1893. SIR JAMES CRICHTON-BROWNE, M.D. LL.D. F.R.S. Treasurer and The Annual Report of the Committee of Visitors for the year 1892, testifying to the continued prosperity and efficient management of the Institution, was read and adopted. The Real and Funded Property now amounts to above 104,000l. entirely derived from the Contributions and Donations of the Members and of others appreciating the value of the work of the Institution. Sixty-three new Members were elected in 1892. Sixty-three Lectures and Twenty Evening Discourses were delivered in 1892. The Books and Pamphlets presented in 1892 amounted to about 238 volumes, making, with 530 volumes (including Periodicals bound) purchased by the Managers, a total of 768 volumes added to the Library in the year, Thanks were voted to the President, Treasurer, and the Honorary Secretary, to the Committees of Managers and Visitors, and to the Professors, for their valuable services to the Institution during the past year. The following Gentlemen were unanimously elected as Officers for the ensuing year: PRESIDENT-The Duke of Northumberland, K.G. D.C.L. LL.D. MANAGERS. Captain W. de W. Abney, C.B. R.E. D.C.L. F.R.S. Sir Douglas Galton, K.C.B. D.C.L. LL.D. F.R.S. Hugo Müller, Esq. Ph.D. F.R.S. The Right Hon. Earl Percy, F.S.A. William Chandler Roberts-Austen, Esq. C.B. Sir David Salomons, Bart. M.A. F.R.A.S. F.C.S. |