a first impression, are not conserved in inert matter; they do not resemble the imprint of a seal upon wax. They are recorded in living matter. Now, living tissues are in a state of continuous molecular renovation, nervous tissue more than any other, and, in nervous tissue, the gray substance more than the white substance, as is shown by the excessive abundance of blood-vessels with which the former is lined. Since the modifications are persistent, the new material, the arrangement of the new molecules, must exactly reproduce the type which they replace. Memory depends directly upon nutrition.

But the cells have not only the power of self - nourishment. They are endowed, at least during a portion of life, with the faculty of reproduction, and we shall see farther on how this fact explains certain cases of restored memory. Physiologists are agreed that this reproduction is only one form of nutrition. The basis of memory is, therefore, nutrition; that is to say, the vital process par excellence.

I shall not now dwell upon this point. When we have spoken of the disorders of memory, its exaltation and depression, its momentary suspension and sudden return, and of its progressive impairment, we may recur to this part of our subject with profit; then the importance of nutrition will be self-evident.

Heretofore we have confined ourselves to preliminary study of memory in a state of health. We must now consider it in a morbid state. The pathology of memory completes its physiology; we shall see if it also confirms it.

CHAPTER II.

GENERAL AMNESIA.

MATERIALS for the study of the diseases of memory are abundant. They are scattered through books of medicine, works on mental disorders, and the writings of many psychologists. They may, with some little trouble, be brought together, and we have then at hand all the facts needed to facilitate investigation. The difficulty lies in classifying them; in giving to each case its proper interpretation; in learning its true bearing upon the mechanism of memory. In this respect, facts collected at random are very unequal in value; the most extraordinary are not the most instructive; the most curious are not the best sources of light. Physicians, to whom we owe them for the most part, have described and studied only from a professional stand-point. A disorder of memory is to them only a symptom, and is so recorded; it serves to establish a given diagnosis and prognosis. It is the same with classification: the

observer is content with associating each case of amnesia with the morbid state of which it is the effect; thus we have amnesia from softening of the brain, hemorrhage, cerebral disturbance, or intoxication.

From our point of view, however, diseases of memory must be studied by themselves, as morbid psychical states, through which we better understand the same elements in a healthy condition. As to classification, we are forced to arrange them according to external resemblances. Our knowledge of the subject is not sufficiently advanced to permit us to undertake a natural classification—that is, by causes. I may state now, to obviate further explanation, that the classification which follows is of value only as it serves to bring a degree of order into a confused and heterogeneous mass of facts, and that in many respects it is entirely arbitrary.

Certain diseases of memory may be limited to a single category of recollections, leaving the remainder apparently intact: these are partial disorders. Others, on the contrary, affect the entire memory in all its forms; completely dissever mental life; produce chasms that can never be bridged over; or demolish it altogether through long-continued activity: these are general disorders. We shall distinguish, then, in the first place, between two great classes-gen

eral diseases and partial diseases of memory. The former only will be considered in this chapter, and will be studied in the following order: 1. Temporary amnesia; 2. Periodical amnesia; 3. Progressive amnesia, the most curious and instructive of all; 4. In conclusion, a few words with regard to congenital amnesia.

I.

Temporary amnesia usually makes its appearance suddenly, and ends in the same way. It embraces periods of time which may vary from a few minutes to several years. The briefest, the clearest, and the most common forms are met with in cases of epilepsy. Physicians are not in accord with regard to the nature, the seat, or the causes of this malady. The solution of the problem is not within the scope or province of this work. It is enough for us to know that all authorities agree in recognizing three forms: grand mal, petit mal, and epileptic vertigo; that these are regarded less as distinct varieties than as different degrees of the same morbid state; and, lastly, that the more moderate the attack in external manifestations the more fatal it is to the mind. The attack is followed by a mental disorder which may reveal itself in odd or ridiculous acts or in crime. All of these acts have a common characteristic, des