Irritability

CHAPTER I. The History of the Subject

THE HISTORY OF THE SUBJECT

Contents: Introductory. Earliest period. Francis Glisson as founder of the doctrine of irritability. Albrecht von Haller. The vitalists. Bordeu and Barthez. John Brown’s system. Johannes Müller and the specific energy of living substance. Rudolf Virchow’s doctrine of the irritability of the cell. Discovery of the inhibitory effects of stimulation. Weber, Schiff, Goltz, Setschenow, Sherrington. Claude Bernard studies on narcosis. Tropisms. Ehrenberg, Engelmann, Pfeffer, Strassburger, Stahl. Semon’s speculations on mneme.

Irritability is a general property of living substance but not exclusively so. Irritable systems also exist in inanimate nature. What characterizes living substances is not irritability as such, but an irritability of a specific type. The irritability of the living system can, therefore, not be studied alone, but as the properties of a living system are dependent upon each other, so this property must be considered with the others possessed by a living substance. In this sense irritability presents a problem of fundamental physiological importance. For if we could analyze the irritability of living substance to its essence, then the nature of life itself would be fathomed. The analysis of irritability of living substance offers us, therefore, a path to the investigation of life and herein lies the importance of the study of irritability.

I wish to follow this path toward the knowledge of the vital processes and to endeavor to show in these lectures what information the analysis of irritability and that of the effect of stimuli can give us of the mechanism of the processes in living substance. Before doing so, however, I wish to consider somewhat more in detail the question as to how we have arrived at the conception of the nature of irritability.

To the thinkers both in the field of physiology and medicine of ancient and mediæval times the conception of irritability was quite foreign. Even a comprehension of the nature of stimuli had not yet begun to crystallize from vague impressions of the various influences of different agents on the human being. Nevertheless they knew of such influences of the most varying kinds upon the human body. The ancients already possessed a materia medica, founded on the real or supposed influence of various mineral, vegetable and animal substances upon the organism. It was also known that heat and cold, light and darkness had an effect upon disease. They likewise believed in the influence of certain factors upon the health of man, which in reality have no effect whatsoever, as the stars and the magnet. But neither in ancient nor in mediæval times was the state of knowledge reached wherein generalizations were made from these agents, which had a real or supposed action upon the organism, and to combine these to a general conception of stimulation.

The conception of stimulation and irritability cannot however be separated.

The founder of the doctrine of the irritability of living substance is Francis Glisson (1597–1677), member of the Collegium Medicum in London and at the same time Professor in Cambridge. It is a fact also not altogether without interest, that Glisson at the same time was in a certain sense a forerunner of those who interpreted nature from a physical standpoint. Glisson as an anatomist and physiologist was an excellent observer and experimenter, but the most prominent trait of his character was his inclination to philosophic observation and analysis of nature. His “Tractatus de natura substantiæ energetica” must, therefore, be considered as the chief work of his life. In this voluminous book Glisson develops an entire system of natural philosophy, which in accord with the character of the philosophy of that time is unfortunately of an absolutely speculative nature and which had hardly emancipated itself from the scholasticism of the preceding period of thought. When the ideas of Glisson are isolated from the wilderness of scholastic phraseology, the system is somewhat as follows. The basis of all existence, “substance,” has according to him two general properties, its “fundamental subsistence,” that is, the essence of its being, and its “energetic subsistence,” that is, the essence of its activity. To these are added the properties possessed in specific cases, that is, its “additional subsistence.” The energetic subsistence forms the basis of all life. Life is therefore present not only in organic nature, but in all nature which is characterized by the union of the general energetic subsistence with the special additional subsistence of an animal and vegetable nature. In other forms of life in nature the energetic subsistence is combined with other special forms of the additional subsistence. The universal essence of all life, that is the energetic subsistence, has only three fundamental faculties: the “appetitiva,” the “perceptiva” and the “motiva.” The modus is the result of a “perceptio,” but the “perceptio” is not thinkable unless the object has the “appetitus” to receive the external influence. Glisson’s doctrine of irritability is based on this conception, which he develops in a second work already begun before the “Tractatus de natura substantiæ,” but not finished until later and only published after his death. In this “Tractatus de ventriculo et intestinis,” Glisson dwells in detail on the physiological properties of animal structures and develops for the first time his conception of irritability in the chapter “De irritabilitate fibrarum.” The “irritability” manifests itself in the appearance of the alteration of movement, which is brought about by external influences on the animal structure, for: “Motiva fibrarum facultas nisi irritabilis foret, vel, perpetuo quiesceret, vel perpetuo idem ageret.” The fundamental factor of this irritability Glisson attributes to the “perceptio,” which he distinguishes as a “perceptio naturalis, sensitiva and animalis.” The want of clearness produced here by Glisson’s artificial distinctions and mode of expression is in part removed if we endeavor to transfer his meaning into our present methods of thought. This distinction would then simply point out the different means by which the stimuli can reach the irritable structures. The “Perceptio naturalis” is that which today we should call “direct response” to stimulation, that is, the excitation of the fiber by artificial stimuli applied directly to the tissue. Glisson shows here, that the intestines and muscles in the body immediately after death and even when removed from the body can be stimulated to movement by means of corrosive fluids or cold. The “Perceptio sensitiva” is, according to Glisson, the excitation of the fibers by external stimuli which act on the intact body as a whole by way of the sensory nerves. The “Perceptio ab appetitu animali regulata” finally is the excitation by inner stimuli proceeding from the brain. The Perceptio naturalis is possessed by all parts of the body, even the fluids, the bones and the fat. All of them are irritable. But a “vitale” and a special “animal” irritability they do not possess to a perceptible degree. These forms of irritability belong only to the special parts of the body. Here, however, the distinctions made by Glisson, are quite vague and contradictory. In his “Tractatus de ventriculo et intestinis” Glisson sharply distinguishes the “sensatio” from the “perceptio.” The perceptio in itself is not a sensation, for although individual organs of the body are irritable, as they all possess a “perceptio,” they are not in themselves sensitive. The “sensatio,” the sensation, only arises when the external “perceptio” of the individual organs combine through the nerves with the internal “perceptio” of the brain. “Nisi enim percepto externa ab interna simul percipiatur, non est cognitio sensitiva completa.” Sensitivity is, therefore, a special faculty, that is only based upon irritability.

Franciscus Glissonius: “Tractatus de natura substantiæ energetica seu de vita natura ejusque tribus primis facultatibus perceptiva, appetitiva, motiva,” etc. Londini M D C L XXII.

Franciscus Glissonius: “Tractatus de ventriculo et intestinis cui præmittitur alius de partibus continentibus in genere et in specie de iis abdominis.” Amstelodami M D C L XXVII.

I have treated the views of Glisson somewhat in detail for on the one hand this seemed to me to be only due to the founder of the doctrine of irritability, and on the other we have here for the first time, although in somewhat vague and little worked out form, the discovery of a general property of all living substance, and its fundamental importance for the life of the organisms. One might, therefore, in a certain sense, date from Glisson the beginning of general physiology, and all the more so, because Glisson from the very first connected the irritability of the living substance through its possessing universal energy with the phenomena in nature generally, just as we do today two hundred years after, on the basis of the modern teachings of energy.

It might appear strange that a teaching of such fundamental importance as that of Glisson’s theory of irritability was not at once accepted on all sides and further developed. There were two reasons, however, which prevented this. Firstly, Glisson did not devote himself to his post of teacher at the University of Cambridge with any particular zeal and so consequently did not establish a school of his own, to further work out and develop his ideas. Secondly, his doctrines were so speculative and difficult to understand, his differentiations and definitions so artificial and labored, that it required the greatest effort to penetrate to his fundamental conceptions and so it happened that Glisson’s theory of irritability received attention only at a comparatively late date. Even then, of his speculative theories hardly more than the name “doctrine of irritability” was adopted. Since the middle of the eighteenth century this name, however, was destined to lead to excited controversies.

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