Keith Lucas. The Conduction of the Nervous Impulses, London 1917. pp. X + 102. Monographs of Physiology edited by Ernst Starling.

Recently, in England, on the initiative and under the direction of the well-known physiologist E. Starling, monographs have been appearing devoted to particular questions of physiology. These monographs do not have the task of giving a formally exhaustive literary survey of the question treated; their aim is different: they are to present a brief and clear account of the results achieved in the given field. In Starling’s view, the exposition should be authoritative; the reader should receive the material at first hand, and therefore the preparation of the monographs is entrusted only to those authors who have worked independently and productively in the given field and are masters of their subject. Altogether, about 10 monographs have so far appeared on the most varied and interesting topics, for example, W. Gaskell—The Involuntary Nervous System, S. Sherrington—The Physiology of the Reflex Arc, W. Bayliss—The Vasomotor System, and others.

K. Lucas’s monograph is devoted to one of the cardinal questions of physiology—the question of the conduction of nervous excitations—and rests above all on the work of Lucas himself and his collaborators. The conduction of the nervous impulse is considered by Lucas exclusively within the limits of the peripheral nerve fiber and of the mechanism of transmission from the nerve to the muscle fiber. But even within these limits the question is not treated in its full entirety, being restricted only to that circle of phenomena which, on the basis of the study of the peripheral apparatus, is capable of illuminating the whole complexity of impulse conduction in the central nervous system; in this narrowing of the task, and at the same time in the seriousness of its conception, lies a certain special interest of Lucas’s monograph. The starting point of the study is the question of the subordination of the nerve fiber to the law of “all or nothing” and of the presence, in the process of excitation, of a “refractory period.” It was first proved on the heart muscle that the degree of its contraction, other conditions being equal, is the same—

regardless of whether it is stimulated by a strong or a weak stimulus—the muscle contracts maximally or does not contract at all. It is further clarified that from the moment of excitation a state of inexcitability is established in the cardiac muscle, and this period is called the refractory period. It is now becoming more and more evident that the “all-or-none” law and the presence of a “refractory period” are universal; that all excitable formations are subject to them to a greater or lesser degree, and, in particular, all links of the neuromuscular apparatus. Thus, if a nerve fiber has received a stimulus, it responds to it with a maximal degree of excitation, which under normal conditions runs at a definite speed without any loss, chiefly from point to point. It is enough, however, to place some part of the nerve under abnormal conditions—for example, to cool it or subject it to the action of alcohol, ether, and the like—and the properties of decrement are at once revealed; that is, the excitation in the altered part runs while gradually diminishing, and may in this way either die out or, if the length of the segment possessing the property of decrement is small, reach, in its course, the normal part of the nerve and there flare up again with maximal force. The excitation of each point of the nerve undergoes in time various phases, both in the normal part of the nerve fiber and in the part burdened by decrement: the first phase has already been mentioned—this is the refractory period, the period of complete extinction of excitability; then there follows a gradual restoration to the initial state, and, as a final phase, there appears a temporary increase of excitability. The first seven chapters, that is, almost half of the book, are devoted to the description and elucidation of the indicated aspects of the vital manifestations of the nerve fiber. The second half contains Lucas’s facts and hypotheses, which are to explain the phenomena of summation and inhibition in the neuromuscular preparation. The central point of the author’s views on this question is his assertion that the summation and inhibition observed in the neuromuscular preparation (Vvedensky’s phenomenon) take place in the transmission apparatus between nerve and muscle, and that the fundamental peculiarity of this connecting apparatus is associated with the presence in it of decrement for the passing process of excitation. Here, in this labile link, inhibition may under certain conditions appear against the background of decrement; here also, under other conditions, as a consequence of the utilization of phases of increased excitability, summation of excitations running one after another is possible as a result. Everything depends on the frequency of the impulses that must be passed by the transmitting mechanism. The author examines in great detail the peculiarity of that mechanism by virtue of which, through a mere change in the frequency of impulses of the nerve fiber, one may produce an increase or decrease in the activity of the muscle connected with the nerve. In Lucas’s opinion, the phenomena of summation and inhibition, which constitute the basis of that background upon which the processes of excitation are played out

in the central nervous system conceal nothing specific and represent phenomena of the same order as summation and fatigue in peripheral excitable tissues. The connecting apparatus between nerve and muscle, in its properties, resembles the synapse, the place of contact of the processes of two neighboring neurons in the central nervous system; the peripheral apparatus has, however, the advantage that it is more accessible to experimental influence and is therefore a rewarding object of study, which will elucidate not only the poisoning of the peripheral but also of the central nervous system.

Lucas’s book appeared after the author’s death. The young and talented scholar, aged 34, perished in 1916 in an aeroplane accident, while serving as a worker in selection during the World War. He made flights in an aeroplane for experiments with a barometer improved by him. The manuscript, not completed by him before his death, was edited by his closest collaborator and friend Adrian.

A. Galambos.