I

RETENTION AS A BIOLOGICAL CONCEPTION

WHEN Prof. Ewald Hering read his paper 'On memory as a Universal Function of Organised Matter' to the Imperial Academy of Science at Vienna, 30 May 1870, he made Memory a biological problem, and such it has remained. One may question whether this presentation left the old memory problem of epistemology and psychology untouched, whether it replaced it, in the sense of substituting a wider for a narrower issue, or whether it merely put the old problem of the philosophers in a new light? It is therefore worth while to follow out the issues raised by Hering's paper. It was new to conceive of one function, reproduction, as the ground not only of memory, but of all increase in facility, of all material growth, and, further, to see in such a function the explanation of ontogeny and of the inheritance of acquired characteristics. Memory for Hering is the Urvermögen which links the phenomena of the body and the phenomena of the mind into one single series.

"Between the "me" of to-day and the "me" of yesterday lie night and sleep, abysses of unconsciousness, nor is there any bridge but memory with which to span them.... The bond of union, therefore, which connects the individual phenomena of our consciousness lies in our unconscious world; and as we know nothing of this but what investigations into the laws of matter teach us-as, in fact, for purely experimental purposes, "" matter and the "unconscious" must be one and the same thing-so the physiologist has a full right to denote memory as, in the wider sense of the word, a function of brain substance, whose results, it is true, fall, as regards one part of them, into the domain of consciousness, while another and less essential part escapes unperceived as purely material processes.' (Translation from Hering in Unconscious Memory, S. Butler, ch. vi, PP. IIO, III.)

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Hering states the now thorny doctrine of the inheritance of acquired characteristics with the utmost simplicity, and, one may add, utmost clearness in the following passages:

We have ample evidence of the fact that characteristics of an organism may descend to offspring which the organism did not inherit, but which it acquired owing to the special circumstances under which it lived; and that, in consequence, every organism imparts to the germ that issues from it a small heritage of acquisitions which it has added during its own lifetime to the gross inheritance of its race. Many mystical theories have been propounded for the elucidation of this question, but the following reflections may serve to bring the cause nearer to the comprehension of the physiologist. The nerve substance, in spite of its thousandfold subdivision as cells and fibres, forms, nevertheless, a united whole, which is present directly in all the organs-nay, as more recent histology conjectures, in each cell of the more important organsor at least in ready communication with them by means of the living, irritable, and therefore highly conductive substance of other cells. Through the connexion thus established all organs find themselves in such a condition of more or less mutual inter-dependence upon one another, that events which happen to one are repeated in others, and a notification, however slight, of a vibration set up in one quarter is at once conveyed even to the farthest parts of the body. With this easy and rapid intercourse between all parts is associated the more difficult communication that goes on by way of the circulation of sap or blood.' 'An organised being, therefore, stands before us a product of the unconscious memory of organised matter, which, ever increasing and ever dividing itself, ever assimilating new matter and returning it in changed shape to the inorganic world, ever receiving some new thing into its memory and transmitting its acquisitions by way of reproduction, grows continually richer and richer the longer it lives. Thus regarded, the development of one of the more highly organised animals represents a continuous series of organised recollections concerning the past development of the great chain of living forms, the last link of which stands before us in the particular animal we may be considering. . . . He who marvels at the skill with which the spider weaves her web should bear in mind that she did not learn her art all on a sudden, but that

innumerable generations of spiders acquired it toilsomely and step by step-this being about all that, as a general rule, they did acquire.' 'All this is as wonderful as when a greyhaired man remembers the events of his own childhood; but it is not more so.' (ibid., pp. 118, 125, 129, 123.)

It was as a contribution to the theory of evolution that Hering's paper attracted attention in this country. Prof. Ray Lankester drew attention to it in a letter to Nature, 13 July 1876. Samuel Butler welcomed Hering as a champion of the theory of evolution which he, in total ignorance of Hering's paper, had set forth in his book, Life and Habit, 1877; and it is in virtue of this teaching that he incorporated a translation of the paper in his book, Unconscious Memory, 1880. The significance of Hering's teaching in this direction, however, must not blind one to the wider question suggested by the title, Memory as a Universal Function of Organised Matter'. Memory is not merely a term to denote a given collection of facts, but is used as an explanatory principle. Advance of the race, reproduction of one generation by another, material growth, increase in skill, recollection of the past, these are all explained by that function which is universal in organized matter: memory. If one tries to generalize these very diverse facts and regard them as a class one may term them each and all ' after-effects' of stimulation. They are for Hering' reproductions' of an original effect which he conceives as retained, and it is Memory which makes the retention of the effect and its reproduction possible. He conceives that' after both conscious sensation and perception have been extinguished, their material vestiges yet remain in our nervous system by way of change in its molecular and atomic disposition'. Presumably what was true of the nervous system was regarded as true of those simpler phases of organic matter of which Hering speaks. The aftereffects' of stimulation would be retained as change in the molecular or atomic structure of fibre and cell. As Butler

comments in a foot-note to his translation of a relevant passage,

Memory was in full operation for so long a time before anything like what we call a nervous system can be detected, that Prof. Hering must not be supposed to be intending to confine memory to a motor-nervous system. His words do not even imply that he does, but it is as well to be on one's guard. (ibid., p. 115.)

Butler, indeed, seems to have some difficulty with Hering's presentation of his doctrine, and inserts frequent foot-notes to correct his author's wording to what he conceives to have been his intended meaning, or rather, perhaps, to what he conceives ought to have been his meaning. The difference between the two is not unimportant. Hering gives a ́ structural' conception of retention, and Butler corrects this to a' functional' conception. This difference in conception will be touched on later.

Hering limited memory to organized matter, but if a molecular or atomic change be the central fact of the phenomena grouped together as after-effects' of stimulation, then changes in the physical and chemical properties of bodies, e. g. in elasticity or conductivity, in consequence of repeated use, should also be regarded as due to memory. (Cf. L'Évolution de la Mémoire, H. Piéron, 1910.) We will consider the implications of Hering's theory in the work of his lineal successor, Dr. R. Semon. (Die Mneme, 3rd ed., 1911.) Semon uses the term ' Mneme' for memory in Hering's sense, viz., a general function of all organic matter, and he tries to establish the general conditions under which such a memory occurs. Human memory is but a special case of Mneme, and is dealt with in his book, Die mnemischen Empfindungen. The central fact to be explained is the reproduction or return of some response when the original conditions which gave rise to it are not repeated in their entirety. The problem embraces both the reproduction of response to stimulation