Fatigue, by J. Joteyko, 1904

Reading report published in the Journal of Normal and Pathological Psychology, Volume I, 1904, p. 46-49 [this is the first text published under the author name “Jean Paulhan”].   See the original in Gallica

in: II. Studies on the nervous system (anatomy and pathology)
(9) — Fatigue, by J. Joteyko, Dictionary of Physiology, vol. VI. fac. 1, 1903 (185 pages).

An organism or animal tissue, when subjected to excitations of long duration or high intensity, causing a strengthening of vital phenomena, falls after a while into a state of fatigue. The effect of excitation then becomes weaker and weaker, although the intensity of the exciting remains constant. We can therefore consider fatigue as a reduction or loss of irritability through excitement: this phenomenon, which can be found even in the plant kingdom, is characterized, in the animal kingdom, by the reduction or total loss of the specific energy of the tired organ (loss of conductivity for the nerve, etc.); the living matter also remains sensitive, within certain limits: 1° to the quality of the exciting; 2° to the intensity of the stimulus. Here the question arises “inactive” excitations, exhausting when they affect an organ fresh (exp. Richet, Joteyko), without physiological effect on an organ already tired.

Taken to the extreme, fatigue can produce death. The organism, for who she is a danger, will have two methods of defense against her: the first relies on the mode of distribution of fatigue itself; the most common organs important (nerve centers) are protected thanks to a certain hierarchy tissues with respect to fatigue (greater fatigability of the terminal nervous system). The second defense process is habituation, that is to say the adaptation of the organism to the stimulus.

CHAP. I. Fatigue of the nerves. — Alongside a first series of experiments (Bernstein: electrotonization of the nerve. Bowditch: transient curarization, etc.) which seem to prove the indefatigability of the nerve, we place it others which, for their authors, demonstrate greater fatigue of the nerve trunk than of the muscle (Herzen, Schiff). Of all the discussions, from the controversies which took place on this subject and which J. recalls at length, two conclusions can be drawn: the absolute indefatigability of the nerves is dismissed, as incompatible with biological laws — certain experiments also prove that the nerve trunk is not exempt from fatigue—but the resistance to fatigue of the nerve remains none the less incomparably greater than that of muscle, less perhaps by a very slow disintegration than thanks to a very rapid reintegration. In ending, the author examines the question of chemical phenomena and their nature in the fatigue of the nerves.

CHAP. II. Fatigue of intramuscular nerve endings. — J. criticizes most experiments based on these two points that the electric current applied to the nerve trunk fatigues the endings nerves without altering the nerve itself, and that the muscular substance is directly excitable by the induced current. From his personal experiences the author draws this conclusion that the phenomena of neuro-muscular fatigue arrive after the same time, either when the nerve is excited or when excites the muscle. On the other hand, after the muscle has become completely enervated by the fatigue of the nervous element, there is still persistence of idio-muscular contraction: we can therefore conclude, on this second point, that there is greater resistance to fatigue of the muscle fiber: an extreme degree of fatigue for the nerve endings is only one average degree of fatigue for muscle fiber. J. explains this point by the fact that fatigue primarily abolishes excitability (including conductivity) of the nerve element contained in the muscle. This muscle tired is therefore an enervated muscle; but the muscular substance retains still its excitability, if it has lost its conductivity (dromotropic action of fatigue): by an appropriate stimulant, acting directly on the muscular substance, we can therefore awaken the contractility which is specific to muscle tissue when directly excited. Then appears the idio-muscular contraction, strictly localized at the excited point.

CHAP. III. Muscle fatigue. — I. General physiology and physics tired muscle: the author successively studies the effects of fatigue on muscle consistency, cohesion, elasticity, modification of characters of contraction in ergographic curves, (exp. Mosso. Joteyko, etc.), the effects of fatigue on muscular strength and work mechanics (e.g. Weber, Maggiora, etc.) on muscle thermogenesis (muscles elongated under the influence of fatigue shorten and heat up less, with equal lifting of loads, than when they have their normal length), finally on electrical phenomena and the death of muscle. — 11. Influence of muscular fatigue on circulation and respiration: J. examines the various explanations that have been given for the phenomena of cardiac and respiratory acceleration which accompany work. While the respiratory acceleration seems due to excitement chemical of the respiratory centers by the modified blood, the cardiac acceleration appears as a nervous phenomenon, at least in the normal work. —111. Influence of modifying agents on muscle fatigue. Are studied successively: the influence of temperature on fatigue, anaerobism in fatigue, the influence of pharmacodynamic agents and poisons (alcohol, whose dynamic action is due to central influence, sugar, caffeine, etc.). — IV. Chemistry of tired muscle; muscle fatigue is accompanied by an increase in acidity of the muscle. The glycogen reserve decreases, the organic phosphorus contained in the aqueous extract of the muscle decreases within very wide limits. There is in all cases disassimilation of albuminoid materials, and these are the products of this disassimilation, sometimes very toxic, which constitute the origin of fatigue symptoms.

CHAP. IV. Fatigue of the spinal nerve centers. — After recalling and criticizing the experiences of Horsley and Waller, the author explains his personal research. They consisted of studying the resistance of spinal nerve centers fatigue it: 1° by means of electro-tonation of the nerve; 2° by means of etherization of the nerve; 3° by means of strychnization of the cord and etherization of the nerve. It seems necessary to admit, according to these experiences, the principle of great resistance to fatigue of the spinal nerve centers. Its immediate cause remains to be determined.

CHAP. V. Fatigue of voluntary movements. — J. recalls Féré's experiments on the dynamogenic influence exerted by intercurrent excitations: the movement of a member other than the one working must have the same influence, by evoking motor representations in its center. Based on this fact, the author distinguishes two sensory-motor types in taking as a measure the accomplishment of work which, depressing for certain subjects, is exciting for others (dynamogenic type characterized by the increase in muscular energy of the limb which did not participate in the ergographic work; inhibitory type characterized by a reduction, in this limb, of muscular energy and sensitivity). For more considerable effects, the difference between the types disappears and the work always produces a reduction in strength. Fatigue then appears: it is characterized by an incoordination of the movements of the two voluntary centers and by a reduction in the precision of these acts. But training, by substituting the action of the will, subject to fatigue, the reflex action which can continue in a manner approximately indefinite, allows you to escape fatigue.

The author further examines the question of the seat of fatigue of voluntary movements. Based on the data from the ergograph he manages to establish the law of the fatigue quotient ratio H/N between the total height uplifts and their number in an ergographic curve: “This quotient which, under identical circumstances, is constant for each individual, undergoes a progressive decrease in the ergographic curves which follow each other at regular and insufficient time intervals to ensure complete restoration from one curve to another.” He leaves follows that the fatigue of voluntary movements first invades the peripheral organs, because of the two constituent factors of the quotient of fatigue, the first (height) is a function of the work of the nervous centers volunteers. The nerve centers are therefore more resistant than the muscles to fatigue.

CHAP. VII. Effects of fatigue on psychological phenomena. — So as fatigue slowly accumulates in the body, the feeling of fatigue, which must be distinguished from it, appears suddenly. We can study it, either from the point of view of its relationships with the kinesthetic sense, or from the point of view of its origin, central for Bain and Wundt, peripheral for most contemporary neurologists. J. admits this last hypothesis: nervous effort increases with fatigue (Mosso); the nerve centers seem to have the almost inexhaustible faculty of sending orders to peripheral devices and it is when these devices are stopped what causes the appearance of the feeling of fatigue. Psychomotor function is also protected by peripheral paralysis. The movement is defended at its highest and most complex.

In certain pathological conditions, the feeling of fatigue is exaggerated (neurasthenia). In other conditions it may be completely lacking. (Hysterical contractions. Exp. Féré, Binet). Finally J. briefly recalls the psychic experiments which aimed to search for the effects of fatigue on reaction times and attention.

CHAP. VII. Intellectual fatigue. — Intellectual work is subject to the same laws as physical work. Intellectual fatigue may thus be studied, either by the pathological method, or by the method experimental. J. reviews the most salient facts provided by these two methods.

The influence of intellectual fatigue on the heart, capillary circulation and blood pressure can be summarized as follows: 1° Intellectual effort energetic and short produces a very clear excitation of the circulatory and respiratory functions, then a slight slowing down of these functions; 2° one intellectual work lasting several hours with relative immobility of the body produces a slowing of the heart and a reduction in peripheral capillary circulation. But the fatigue caused by intellectual work does not simply remain central: it affects the motor nerves and the muscles; and it is therefore a physiological error to want to rest from intellectual work to physical work. As for the influence of intellectual fatigue on tactile sensitivity, it seems very clear (Exp. Griesshach.): Mild fatigue is usually accompanied by hyperesthesia; stronger fatigue from anesthesia, at the same time as more great sensitivity to pain.

CHAP. VIII-IX-X. —In the last chapters, after having referred, for the study of sensory fatigue, to the special dictionary articles on the senses, J. studies the microscopic phenomena of fatigue: influence fatigue on the protoplasm, on the internal structure of the nerve cells (reduction or retraction of the cell body, reduction in volume, core deformation); finally on the external modifications of the cells: appearance of pearls or varicosities along the nerve extensions, disappearance of the pyriform appendages. (Exp. of Stefanowska.) The latter chapter, which falls into the field of pathology, gives a short overview of overwork, whether physical or mental, and its pathogenic role.

Jean PAULHAN.