unconnected with that in question. This applies also to more complicated mental operations. Sir B. Brodie (Psychological Inquiries) alludes to this subject in the following terms:- "It has often happened to me to have been occupied by a particular subject of inquiry; to have accumulated a store of facts connected with it; but to have been unable to proceed farther. Then, after an interval of time, without any addition to my stock of knowledge, I have found the obscurity and confusion cleared away; the facts seemed to have settled themselves in the right places."

Dr. Carpenter (Human Physiology, 608-9), in treating of this phenomenon, observes :-"The entirely new development which the subject is frequently found to have undergone, when we return to it after a considerable interval, cannot be reasonably explained in any other mode than by attributing it to the immediate activity of the cerebrum, which has in this instance automatically evolved the results, without our consciousness. ... It is difficult to find an appro

priate name for this class of operation. They can scarcely be designated as reasoning processes, since 'unconscious reasoning' is a contradiction in terms. The designation unconscious cerebration' is perhaps less objectionable than any other."

In the dialogue between Mephistopheles and Wagner (see Göthe's Faust) the inquisitive student is strongly advised "to stick to words." But, says the anxious scholar, "there must be a notion attached to the word." Meph. "To be sure there ought; but you must not be too nice about that; for just where our notions are wanting a word will help us out." Now, with all due deference to Dr. Carpenter, we must confess that " unconscious cerebration" seems to us an expression utterly devoid of any meaning. We apprehend that in a "cerebration" there must be something which" cerebrates," and something which is "cerebrated;" but, to use a popular expression, we are at a loss to conceive "which is which." But was there really any necessity for coining a new term for that mental process by which the automatic action of the brain, apparently without our knowledge, selects, aggregates, and eliminates facts and events? We think not. To be sure, the assumption of the automatism of the brain smacks somewhat of sensualism, the modern name for materialism,-which broadly assumes that just as it is the function of the liver to secrete bile, and of the lachrymal gland to secrete tears, so it is the function of the brain to secrete thoughts. But whether we assume that the process is effected by the mind acting on and through the brain, or that the

latter acts automatically, the psychical phenomenon of a train of ideas being unconsciously evolved, once the impulse being given by a sensation or an idea, must be admitted as an ultimate fact, explain it as we may. These phenomena appear to us to pertain altogether to the law of association, which extends to all of our ideas, sensual, intellectual, emotional, and volitional. By association, under the laws of resemblance and contiguity in time and place, our ideas are regulated, linked together, and may be called up together. It has been said that it is to the mind what the law of attraction is to matter, drawing together ideas connected by affinities, and repelling others that cannot coalesce. The greatest confusion would prevail in our minds; our memory would be a lumber room, not a store house, were there not a fundamental principle at work which introduces some order among the myriads of our ideas. It is an automatic process not necessarily attended by consciousness. It is independent of our will; for though we have, in the waking state, considerable control over our association, we cannot altogether emancipate ourselves from its direction. Ideas which we would rather discard will start up, in spite of our efforts to suppress them.

And may we not, since it is permissible to theorize, in the absence of positive data, explain the spoken of psychical process in this way, viz., that whilst we use one hemisphere or one brain, in the elaboration of a fresh subject of thought, we leave the other brain to its own automatic action, that is to the association of ideas, in the evolution of which it will sometimes succeed more effectually when let alone than by the interference of the will, for it is frequently this very interference which defeats our object.

The Cerebellum. This organ is anatomically so distinct from the cerebrum, with which it is but slenderly connected at the base, that one would think that there could be no difficulty in assigning to it a special function; yet even here the theories are conflicting. There are comparatively few authors who have assigned to the little brain. any participation in the higher psychical manifestations. Amongst modern physiologists we may mention Carus, who considers it as the seat of the will and desires; whilst Jessen deems it as the special organ of the emotions. Dugés (Traité de Physiologie) thought it was an organ of the perception of taste and hearing. Gall again, and his followers considered the cerebellum as the exclusive seat of sexual desire. Rolando looked upon the cerebellum as the central source of all voluntary motion. Magendie thought that this organ impels the animal forward, and thus was the antagonist of the corpora

striata, which induce the animal to retrograde. Flourens, Hertwig, and other experimentalists, only looked upon the cerebellum not as the source, but as the regulator of voluntary motions, inasmuch as animals deprived of this organ are still able to move, but cannot maintain their equilibrium. This theory of considering the cerebellum as the co-ordinator of voluntary movements, which had received the assent of most physiologists, is again contested by several eminent authors. Brown-Séquard also denies that the guiding power has its seat in the cerebellum. "I have ascertained, he observes, that by the irritation they produce on various parts of the basis of the encephalon, that the diseases of the cerebellum or its extirpation in animals cause the disorder of movements, which has been considered as depending upon the absence of a guiding power. In fact the least irritation of several parts of the encephalon, with only the point of a needle, may generate very nearly the same disorder of movements that follows the extirpation of the cerebellum. I have been led to conclude that after this extirpation, or after the destruction by disease of a large or small part of this nervous centre, it is not its absence, but some irritative influence upon the parts of the encephalon that remain unaltered which causes the irregularity of movement."

"The cause of the co-ordination of muscular movements is" (says Schroeder van der Kolk)" situated in the spinal cord, and it has always been incomprehensible to me how any one could ever have referred it to the cerebellum. If the cause of co-ordination lay in the cerebellum no harmonized reflex movements could take place in a decapitated frog. . . . . If the cerebellum were the seat of coordination, irregular movements would of necessity ensue, on an irritation of that organ. But in ulceration of the cerebellum, when the irritation is more chronic and not so violent, I have never seen irregular movements arise."

No wonder that the most recent writer on the physiology of the nervous system, Moritz Schiff, an experimentalist of considerable eminence, has arrived at the conclusion, that for the present, the real functions of the cerebellum are altogether unknown.

We have hitherto considered the hemispheres as the sole organ of the mind in man. Doubts have, however, long existed against the generally received opinion that the hemispheres properly so called constitute the only sensorium-the exclusive seat of consciousness. Modern experimenters have, therefore, endeavoured to establish the sensorial functions of certain ganglia in the centre and at the base of the brain; others in the medulla oblongata; and, finally, some in the spinal cord.

"I consider," says Lotze (Medicinische Psychologie-Medical Psychology, 1852), "the corpora striata, the optic thalami, the tubercula quadrigemina, the pons, and the cells in their neighbourhood, as that series of organs in which the combination of sensual impression, and the excitation of co-ordinate motion take place, and that these parts may exclusively be considered as the 'organ of the soul.' To ascribe to each of these parts its proper functions we possess no exact data, except the blindness which seems to result from injury to the tubercula quadrigemina, and the disturbed co-ordination of motion, in consequence of the destruction of the optic thalami, and of some parts of the cerebellum. To consider so large an organ as the cerebellum the exclusive seat of sexual desire seems to me an absurd idea. I dissent, therefore, from all such fancies as to place intelligence in the cerebrum, the will in the cerebellum, and the emotions in the mesocephale."

Lotze further thinks that the hemispheres cannot be considered as exclusively the seat of intelligence, inasmuch as large quantities may be lost without interfering with psychical phenomena, and that there are instances on record in which the loss of cerebral substance has, after the cure, rendered the mental operations more active, and the temperament more lively than it was before the loss. He considers, therefore, the hemispheres, specially the cortical portion, as a nutrient organ for the nervous principle of the organs of sense. But though they have no direct influence upon sensation and recollection, the hemispheres may in one aspect be considered as an organ of intelligence, because they determine the force and functional capacity of the nerves, and possess thus a great influence upon the energy of sensation, emotion, and temperament. Dr. Carpenter, as is well known, has long advanced the same theory, giving to the above-mentioned structures the name 'sensory ganglia', instead of sensorium commune.

Thalami Optici. From experiments performed to determine their functions, it seems that these bodies are not, as the name implies, essential to vision, for they have been destroyed without any loss of the power of sight. According to Longet the optic thalami seem to have a crossed action upon the voluntary movements. Destruction of the right thalamus has the effect that the animals fall at once upon the left side, and if the left be destroyed a similar debility is manifested in the right side. The removal of either of these thalami may also produce effects similar to those observed in the division of one crus cerebri, namely, a rotatory motion, the animal turning continually round. The real functions of these bodies are,

however, not satisfactorily proved; nor is this surprising, as they can neither be isolated nor entirely removed, without injuring the adjoining parts.

The terms tuber annulare and pons varolii are by many anatomists used synonymously; others apply the latter term only to the transverse fibres forming the commissure between the hemisphere of the cerebellum, and tuber annulare to the projection from the surface of the medulla, which contains a considerable quantity of vesicular matter; hence they consider this part as a special centre of sensation and motion. The experiments of Longet and Flourens show that even after complete removal of the encephalon above the medulla in warm-blooded animals, leaving the pons intact, there still remain indications of sensibility and voluntary motion, which cease on the destruction of the tuber annulare. The animal may still be induced to move by external irritation, but these movements seem rather due to reflex action of the spinal cord than to volition. The tuber annulare is, therefore, by some physiologists, considered as an organ by which impressions are conveyed inward, are converted into sensations, and where voluntary impulses originate, stimulating the muscles to contract.

Tubercula Quadrigemina. These are four round eminences, placed in pairs, two in front and two behind. The anterior pair, the nates, are longer than the posterior pair, the testes. Both pair are solid in the adult, and composed of white matter externally, and grey matter internally. That these bodies are closely connected with the sense of sight can be proved by direct experiment. Section at any point of the optic nerves to which they give origin, between the retina and the tubercles, produces complete blindness, whilst injury or destruction of the tubercles themselves produce the same effect. Besides being the nervous centres for the perception of light, a reflex action takes place through them to the iris, to regulate the quantity of light admitted to the eye, by the dilation or contraction of the iris. Dr. Laycock (Mind and Brain) dissents from this. "It is far more probable," he observes, "that the tubercula quadrigemina belong to the medulla, and may be considered to be co-ordinating structures for the substrata of the muscles of the special senses, including touch. In the mole, with rudimentary optic nerves, these tubercles are of immense size. This fact is of itself sufficient to disprove the theory as to the functions of these bodies."

Corpora Olivaria. Dugés (Physiol. Compar., 1838,) observed:"The olivary bodies possess another interest, as nervous centres. It