a deep impression on her mind. The period of her residence in Edinburgh had been uniform and tranquil, and without any occurrence calculated to excite much attention in a person of rather slender mental endowments. I do not know whether we can give a similar explanation of cases in which the loss of memory has extended only to particular subjects; namely, by supposing that these subjects had been more slightly impressed upon the mind than those which were retained. A gentleman is mentioned by Dr. Beattie, who, after a blow on the head, lost his knowledge of Greek, and did not appear to have lost any thing else.

While we thus review the manner in which the manifestations of mind are affected, in certain cases, by diseases and injuries of the brain, it is necessary that we should refer briefly to the remarkable instances in which the brain has been extensively diseased without the phenomena of mind being impaired in any sensible degree. This holds true both in regard to the destruction of each individual part of the brain, and likewise to the extent to which the cerebral mass may be diseased or destroyed. In another work I have mentioned various cases which illustrate this fact in a very striking manner; particularly the case of a lady in whom one-half of the brain was reduced to a mass of disease; but who retained all her faculties to the last, except that there was an imperfection of vision, and had been enjoying herself at a convivial party in the house of a friend a few hours before her death. A man, mentioned by Dr. Ferriar, who died of an affection of the brain, retained all his faculties entire till the very moment of death, which was sudden: on examining his head, the whole right hemisphere, that is, one-half of his brain, was found destroyed by suppuration. In a similar case recorded by Diemerbroek, half a pound of matter was found in the brain; and in one by Dr. Heberden, there was half a pound of water. A man, mentioned by Mr. O'Halloran, suffered such an injury of the head that a large portion of

Applicability of it to other cases? Is disease of the brain always attended by disorder of the mind? Case of the lady. Did she enjoy all her faculties? Case mentioned by Dr. Ferriar. These cases similar, in what respect? Frequency of such cases?

the bone was removed on the right side; and extensive suppuration having taken place, there was discharged at each dressing, through the opening, an immense quantity of matter mixed with large masses of the substance of the brain. This went on for seventeen days, and it appears that nearly one-half of the brain was thrown out mixed with the matter; yet the man retained all his intellectual faculties to the very moment of dissolution; and through the whole course of the disease, his mind maintained uniform tranquillity. These remarkable histories might be greatly multiplied if it were required, but at present it seems only necessary to add the very interesting case related by Mr. Marshall. It is that of a man who died with a pound of water in his brain, after having been long in a state of idiocy, but who, a very short time before death, became perfectly rational.

The facts which have been thus briefly referred to, present a series of phenomena of the most remarkable kind, but on which we cannot speculate in the smallest degree without advancing beyond the sphere of our limited faculties; one thing, however, is certain, that they give no countenance to the doctrine of materialism, which some have presumptuously deduced from a very partial view of the influence of cerebral disease upon the manifestations of mind. They show us, indeed, in a very striking manner, the mind holding intercourse with the external world through the medium of the brain and nervous system; and, by certain diseases of these organs, they show this intercourse impaired or suspended; but they show nothing more. In particular, they warrant nothing in any degree analogous to those partial deductions which form the basis of materialism. On the contrary, they show us the brain injured and diseased to an extraordinary extent, without the mental functions being affected in any sensible degree. They show us, further, the manifestations of mind obscured for a time, and yet reviving in all their original vigor, almost at the very moment of dissolution. Finally, they exhibit to us the mind, cut off from all intercourse with the external world,

Danger of speculating on these facts. Certain inference from them-what? They show us what? Summary of the facts stated in this section.

recalling its old impressions, even of things long forgotten; and exercising its powers on those which had long ceased to exist, in a manner totally irreconcilable with any idea we can form of a material function.

SECTION II.

ABSTRACTION.

BY ABSTRACTION we separate various facts from each other, and examine them individually. We separate, for example, the qualities of a substance, and contemplate one of them apart from the rest. This act of the mind is employed in two processes of the utmost importance. By the one, we examine a variety of objects, select the properties in which certain numbers of them agree, and thus arrange them into classes, genera, and species. By the other, we take a more comprehensive view of an extensive collection of facts, and select one which is common to the whole. This we call generalizing, or deducing a general fact or general principle; and the process is of extensive application in all philosophical inquiries. The particular points to be attended to in conducting it, will come under view in another part of our subject. The most important is, that the fact assumed as general really belongs to all the individual instances, and has not been deduced from the examination of only a part of them.

The process of classification is of so great practical importance, that it deserves to be carefully considered. To show how the definition given above applies, let us take a particular case.

A person has made, we will imagine, a large collection of seashells, which lie promiscuously on tables before him. He proposes to classify them. This, according to the definition, consists "in examining them with reference to selecting the properties in which certain numbers of them agree, that they may be arranged in classes according to their properties."

Let us suppose the property he first examines is color. He looks

Its definition. Classification-what? Generalization-what? Example illustrating the process of classification. Definition--what? How applicable ?

over the whole, and takes out all that are spotted, and places them by themselves. He next takes all which are white, and forms of them another class, and so on, arranging them in classes, according as they agree in the property of color. Or they might, in the same way, be classified with reference to any other property, or, as the more common phrase is, on any other principle. Take, for example, form. All those which are in two parts, as the oyster, the clam, &c., might be arranged by themselves, in one class, and those which consist of a single part, in another. These classes might be easily subdivided on the same principle, i. e., with reference to form alone. All the spiral shells might form one division, the conical ones another, and those of some different form still, a third. This would be classifying them on the principle of form.

Now it must be observed that this classification would entirely break up and destroy the other. For the spotted shells, which were before arranged together, in one class, would now be scattered among several, according to their various forms. In other words, they agreed in the property of color, so that when considering them with reference to color they were put together; but they disagree in respect

to form.

The principle of classification, which is thus adopted in the case of any collection of individual objects, may be varied almost indefinitely. The shells, for example, might be classified with reference to the habits of the animals, i. e., all which lived in fresh water might form one division, and salt water shells another. Each of these might be subdivided with reference to the food or the habits of the animal.

Or the principle of classification might be geographical. Those from Africa might be placed on one shelf, those from Asia on another, and American specimens on a third. Thus the principle might be varied indefinitely.

In determining on the principle of classification to be adopted in any case, that is, the property or peculiarity in which those placed together are to be similar, we must have regard to the object in view. Sometimes it is necessary to classify the same individual objects in several different ways, for different purposes. Words, for example, are classified in a common dictionary with reference to similarity in the initial letters-in a rhyming dictionary, the sound of the last syllable determines their place in a grammar and in a spelling book, two other principles are adopted, entirely distinct from the preceding, and each other. Thus the same things, that is, the words of the English language, are classified on four entirely different principles, according to the end in view.

In some cases it is very difficult to determine what principle of classification will best answer the purpose. A common case of this kind is the question of arranging the books of a library. Shall they

First mode of classification? Based upon what property? Second mode; on what property? Subdivision on the same principle, how effected? Relation of these modes to one another? Extent to which the principle of classification may be varied? Examples. Geographical arrangement? Various classifications of words, why made } Arranging a library; what difficulty?

be classified according to the subjects of the works, or in the alphabetical order of their titles, or in the alphabetical order of the authors' names, or according to the languages or countries in which they were written. It is plain that a library may be arranged in perfect order on each of these plans, though each is entirely different from the rest, and altering the arrangement from one to the other would perhaps change the place of every book in the whole collection. Each, too, would have its ground of preference over the others, depending on the object which the reader has in view in consulting the collection. The advantages of all are sometimes in a good degree secured by arranging the books, on the shelves, on one principle, and making out two or three catalogues, in which the other methods of classification are respectively adopted.

A classification cannot, however, in any case, be carried into full effect, except in the exact sciences; for, from the very nature of the case, the several classes will run into each other, whatever may be the principle adopted, and consequently there will be many individual objects, of which it will be impossible to say unhesitatingly where they belong. Some shells will be neither decidedly white nor deci dedly spotted, but something between. A librarian may be perplexed in considering whether to class Marshall's Life of Washington as history or biography, and a writer on English grammar may, in the same manner, hesitate whether to call a certain word a pronoun or an adjective, when it partakes of the nature of both. This difficulty does not apply to the exact sciences. If a figure is either a triangle or a quadrangle, it will be very clear which of the two it is. It cannot be intermediate. It must have either three sides or four. In the exact sciences, therefore, the classification may be exact, but in others it cannot always be, and in doubtful cases we may arrange the object in either of the classes which seem to claim it. There are often, in such cases, very idle disputes, especially on the subject of grammar. True philosophy, in such cases, requires us to consider either as right, when the nature of the case leaves it doubtful.

These remarks, then, naturally lead us to the following practical rules, which are worthy of very careful consideration, since there is. perhaps no process, a thorough understanding of which is more essential to a well disciplined mind than classification.

1. In determining upon a principle of classification, there should be a careful regard to the object in view, in making the classification itself.

2. The classes should be bounded by as distinct and well defined lines as the nature of the case will allow.

3. The classes should be such as to include all the individuals, i. e., so that every individual object shall belong to some one or other of them.

Various modes. How may they be combined? Difficulty in carrying a classification into full effect. Examples. Exact sciences. Example? Inferences from these remarks? Rules. To the boundaries.