conditions which are not found in the nervous system. The propagation of the nervous force is interrupted by causes which would not produce a similar effect upon the electric current. Matteucci considers the nervous force to be due to "movements in the equilibrium of the ether distributed in the nerves:" and that there exists an analogy between light, heat, electricity, and the nervous force; and that the nervous force is capable of being transformed into electricity, under the influence of a peculiar structure of organs; as exemplified in the muscular actions, and the influence evolved by electric fishes. But the whole of Matteucci's account must be studied, to give a due appreciation of all the beauty and importance of these experiments.

Even more interesting than these, is the issue of a series of experiments which have of late engaged the attention of the venerable philosopher, Humboldt.

Occupied myself," he says* in a letter to Arago, "for more than half a century in this class of physiological researches, the discovery which I have announced has for me a vital interest. It is a phenomenon of LIFE, rendered sensible by a physical instrument." In his Annals of Chemistry for June 1849, Liebig relates a method by which unquestionable results, bearing upon this discovery, were obtained. In order to cause a variation of the magnetic needle, sixteen persons held each other's moistened hands, and simultaneously contracted their right arms;

* Humboldt's First Letter to Arago. 1850.

then simultaneously their left; thus forming a circuit of strong electro-motive power. The effect on the needle was manifest; and opposite, according as the right or the left arm was contracted. The deflection reached 12o, any accidental influences being overborne by the intensity of the current. The aged Humboldt was not satisfied without effecting this result by his own volition. "Notwithstanding my advanced years," he says, "and the little strength I have in my arms, the deflections of the needle were very considerable: but they were naturally more so when the experiment was performed by M. J. Müller, or by M. Helmkoltz, who are younger men." He says that "the fact is established beyond all question of doubt."—What can be more interesting than such a discovery as this? and what more serious and solemn than the indications it yields of new regions of discovery in regard to the essential relations of mind and matter?

But I am extending my notes too far, and must end. I will only advert to the common sense of pain so often experienced from a change of weather. I have a friend who is quite a barometer, and speaks with certainty of change in the weather many hours before it occurs.

Thus I have noted down a few instances which occur to me as matter which may interest you, and as an example of what I think we should collect together in an orderly way, as a true mode of attaining a knowledge of the senses in particular, and the nervous system in general. Men separate the sciences

too much. We must study them in connection, if we would attain to just views, and general laws, and recognize the philosophy of Man in universal nature.

XIII.

H.M TO H. G. A.

Some parts of this last letter of yours please me greatly, and set one collecting one's experiences and old speculations under the new classifications in a way I enjoy. You must know I was a devout student of Hartley, all my youth through; and a clinging believer in him for long after I had passed my youth. It is astonishing to me now that I could admit without question his supposition that Man has two primary powers which are enough to account for everything; the capacity for pleasure and pain, and the principle of association. He does not even seem to think of the desire of pleasure and the fear of pain, which surely do not come under either of his

" If all which I have mentioned is not yet accomplished, it is because, neglecting the useful example of the ancient sages of Greece, men have separated from each other too far physiology, medicine, education, morals and legislation, instead of appreciating their natural relations; and still more, because there are few philosophical physicians, who can embrace the whole extent of their sphere of activity, and elevate themselves to the full dignity of their rank.”—Gall.

two heads. It is the exquisite morale of the man, his heavenly temper and holy conscientiousness, which lead one away to think as he thinks, and feel as he feels. All the while, I was despising the Scotch metaphysicians as I still think they deserve-for classifying and illustrating interminably, without having ascertained any basis whatever. Hartley had a grasp of something, however inadequate: they, of nothing, unless, indeed, it were a clumsy method of declaring that Man has intuitions. In the midst of all this, in the midst of exhibitions of a sort of compartments of an immaterial Mind, called respectively Memory, Imagination, Judgment, and so on, stood out before me suddenly Dr. Thomas Brown's discovery of the Muscular Sense,-a curious piece of reality amidst a symmetrical array of suppositions! After this, one could never more be satisfied to lump together, under the name of one sense, things so different as perceptions of temperature, resistance, muscular ease or ache, and acute physical pain or pleasure, sensations of touch, &c. Now that we are released from the magical number five, in regard to the senses, we are free to recognize things as they are,— to number our faculties, and to enlarge the number, if occasion should arise, by the development of new, -that is, hitherto unknown-faculties, which bear a relation to external things.

It is really vexatious that I cannot convey to you, or any one, what I think I have reason to rely on about this; the existence of some faculty or faculties by which things can be known or conceived of

apart from all aid whatever from the senses which usually co-operate in the presentment of ideas. You know that I preserve some distinct recollections, on awaking from the mesmeric trance, of the ideas presented in that state. Well: twice at least I have perceived matters so abstract as to owe no elements whatever (as far as I could discover) to the ordinary senses. For instance,-I believe there are no persons (not blind) who have any ideas whatever with which visual impressions are not more or less implicated. I have asked everybody, for many years,—everybody whom I thought capable of the requisite consciousness and analysis; and they all tell me that there is nothing so abstract but that they entertain some image inseparably connected with the thought. The days of the week,—the virtues and vices,―numbers, -geometrical truths, even God,-all these have some visual appearance, under which they present themselves, be it only their printed names. I have not had the opportunity of questioning the blind (from birth) about this: but I am assured by some who have, that they have the same experience derived from the other senses than that in which they are deficient. Now, in certain depths of the mesmeric state, I have received knowledge, or formed conceptions, devoid of all perceptible intermixture with sensible impressions. Of course, I cannot explain what they were, because they could be communicated only to a person in a similar state; and not by ordinary language at all. They have since (during five years) been gathering to themselves more and more visual