the same person, according to circumstances. It is positively certain that the sense of smell, like all other senses, can be refined by exercise; we gradually learn more easily to apprehend faint odors-to distinguish between different ones-to recognise the shades of one and the same odor. The nose of a connoisseur of wines boasts of being able to find out the land and the year which have produced a certain wine; the nose of a chemist is in many cases a reliable agent for discovering the presence of smellable chemical combinations. On the other hand, we often meet with a gradually developed obtuseness of the sense of smell, be it in consequence of old age, in which all senses suffer from a decrease of nourishment, of a habitual stuffing of the smelling channel with snuff, or of a diseased condition of the nasal cuticle. That every bad cold carries with it a considerable weakening or temporary loss of our smelling faculty is an experience which few men will not have gained. Some persons are inaccessible only to certain odors, their sense of smell being otherwise in a perfectly normal condition-a partial want, the cause of which is yet unexplained.

We shall say but few words on the aesthetic side of smelling. The opposite conceptions of fragrance and stench denote the fact that certain qualities of smell produce an agreeable, and others a disagreeable sensation. But it is hardly necessary to remark that there is no universally acceptable division of odors, without reference to the nose, into agreeable and disagreeable ones; that one person is delighted by an odorous substance which is loathsome to another; nay, that the same person may under certain circumstances call an odorous substance fragrant, and detest it under others. Habit, custom, bodily conditions, determine and modify the aesthetic effects of impressions of smell. Thousands of persons find the smell of valerian greatly disagreeable, while others rank it, as do the cats, among the perfumes; some are attracted, others are repulsed, by the smell of old cheese or of garlic. Even the most disgusting odors meet with particular favor; there are hysteric ladies to whom the smell of burned hair is incense. The Laplander rejects such tallow as would not, by its rancid smell, stand the test of his nose. It is true, we take the liberty of blaming their taste, or even to class them with the animals on account of this their presumed perverseness; but we do it, perhaps, with no more right than they would have to reproach us for placing musk among the perfumes. Very likely, the esbouquet atmosphere of a European fashionable lady is as distasteful to an Esquimaux as is to us his fish-oil smell, and neither he nor we have a right to declare his or our judgment exclusively acceptable. De gustibus non est disputandum. As regards the change of judgment in the same person concerning certain odors, we have already spoken of that daily experience that in a state of hunger we are powerfully attracted by a smell of food which disgusts us in a state of satiety. Finally, we must also remark that our judgment varies with intensity of an odor; that most persons find a feeble odor of clove oil pleasant, and a strong odor of the same disagreeable, and so on. The mentioned facts admit of no physiological conclusion; we have not yet made the faintest step towards explaining the question how a sensation of smell acts upon our imagination, or on what conditions depends the quality of a feeling produced by smell. It need not be further explained that to call a sensation of smell in itself agreeable or disagreeable is to speak incorrectly. In our introduction we have designated the sense of smell as a tyrant; it is but just that we should represent also its good qualities in their real light, and try to satisfy in our readers the desire of knowing the vocation and functions of that sense. A few hints will suffice; may the reader sketch out to himself the rest. The observation of animals is our best guide for that purpose; in many of them the sense of smell performs a more important, more obvious part than in man, who, if it must be, can even do without it. The finding of their necessary aliment, the discovery of their natural enemies, depends, with thousands of animals, on the services of the organ of smell, and hence the extraordinary fineness of that sense with them. The fox scents a dead body from a

distance of many miles, and finds it by following the smell; the wind conveys to the game the exhalation of man over a large tract of land; it is the smell which, in the pairing season, brings together the males and females of a large number of animals, thus playing an important part also in the preservation of the species. With man, it is true, the functions of the nose are less conspicuous and apparently of less vital importance; but though he makes no use of it for finding out his nourishment or his enemies, still its vocation is not restricted to causing delight to the soul by sweet odors. Is it necessary to adduce special examples to show in how many ways we are indebted to our sense of smell for information regarding the presence or absence of substances or certain proceedings in the outer world, from which all kinds of judgments and actions may occasionally result? We shall specify only one side of our nasal activity. The organ of smell is frequently designated as a guard of respiration, as it informs us about the quality of the air which we inhale, and teaches us to shun certain noxious irrespirable gases, which are distinguished by a peculiar odor. This designation ought not to be misunderstood, nor the importance of that office overestimated. First, there is a number of irrespirable gases which produce no sensation of smell, against the inhaling of which, therefore, the nose is incapable of warning us. Secondly, it must be observed that the quality of a sensation of smell does not directly indicate the noxious or innoxious character of a certain gas, or of a certain admixture in the atmosphere, but that in order to find this out we must have acquired by other means the necessary experience concerning the effects of gases and vapors characterized by peculiar odors. Were we to form our judgment according to an idea immediately attaching itself to our sensation, and thus believe all agreeable impressions of smell to be innocent or useful, and all disagreeable ones to be injurious, we would fall into quite dangerous deceptions; for instance, we would be inclined to sip prussic acid without hesitation. Thirdly, we must still remark that we recognize a number of noxious aerial substances by the nasal sense of touch, and not by that of smell, and that these sensations of touch, on account of their highly disagreeable quality, more easily persuade us to avoid the inhaling of those gases than would the sensations of smell. Those pungent sensations of touch which are produced in the nose by the vapors of sulphur leave us not a single moment in doubt whether we shall inhale those vapors or not, and they would prevent us from inhaling them even if we knew them to be conducive to our health. In this limited sense only the organ of smell deserves the title of guard of respiration.

This much, or rather this little, dear reader, do we know of the sense of smell. We have candidly unveiled the weak sides of physiology, being convinced, as we have stated, that it must be of great use to the common reader to learn what we do not know, and that it is a merit to show the erroneous character of popularly current physiological notions, even when we are unable to replace them by exact truths. May our reader share with us the hope that the power of science, so nobly developed in our age, may once, and perhaps ere long, lift the veil still unpenetrated, and, according to some desponding minds, eternally impenetrable, which covers the mysteries of nervous life. Though the soul, the immaterial principle, must forever remain a noli me tangere of physiological research, the machinery by which it works will once lay open before the eye of physiology with all its innermost recesses and finest particles. We would not like to quarrel with the most genial of our poets, but it grates on our ear to hear Faust thus despairingly speak of nature. What it reveals not to thy spirit thou canst never extort with levers and screws. A little but essential alteration of this sentence will make it the device of the physiologist, with which he will calmly follow the trace of the highest problems. Our device is: Thou must extort it with levers and screws! The microscope, the chemical balance, and other manifold and ingenious apparatus which fill the armory of the physiologist, are our lever, our screw.

ELECTRO-PHYSIOLOGY:

A COURSE OF LECTURES BY PROF. CARLO MATTEUCCI, SENATOR, &c.

TURIN, 1861.

TRANSLATED FOR THE SMITHSONIAN INSTITUTION BY C. A. ALEXANDER,

LECTURE I. Introduction.-Definition of electro-physiology.-Distinction between the electro-physiological effects and the physical and chemical effects of electricity.-Apparatus for experiments in electro-physiology.-Measure of muscular power produced by electricity.

Grateful for the welcome which my auditors extend to this course of lectures, I ascribe their kind reception in great part to the common sentiment by which at present we are all animated. A professor of the University of Pisa, presenting himself as a lecturer at Turin, where at the same time he resides as senator, affords but another and significant token of our national union.

I do not now propose to entertain you with novelties, but I hope to communicate some portion of the warm interest which I feel in one of the most fertile and attractive sciences of modern times, the science of the physico-chemical phenomena of living bodies. It is a science whose discoverers made their first appearance in Italy, where it has since never ceased to be cultivated-a fact which needs no other proof than the names of Redi, Fontana, Spallanzani, and Galvani.

What I have said would have received the assent of that great man, one of the most extraordinary intellects of our century, to whom Lagrange is said to have once made the remark that there could be no further discovery so great as that made by Newton of the law of universal attraction, because there was but one world. There is still another, replied Napoleon-the world of details. This world is peculiarly that of the living organism.

But let us enter upon the subject. What is electro-physiology?

In former times, soon after the discovery of the electrical machine and Leyden jar, such was the wonder excited by the electrical phenomena that to electricity were attributed the most extraordinary effects on animals and on vegetables. Naturally this wonder was not diminished after the discovery by Galvani of the contractions occasioned in the frog by the passage of electricity. It was then the received belief, though founded on mere imagination, that plants electrified grow much more rapidly and luxuriantly than those not thus treated; that the soil might be fertilized by electricity, and that an amalgam of zinc substituted for the brain of an animal could restore its sensibility and intelligence. These presumptions of false science could not fail, of course, to be dispelled by those rigorous experiments which have led in later times to the foundation of the science of electro-physiology, a part of physics which has established certain laws on well-demonstrated facts, and has also advanced some hypotheses which are found to interpret a considerable number of those facts.

Electro-physiology falls readily under two divisions: the action of electricity on vegetables and animals-an action manifested by appropriate effects relative to the vital organism-and the development of electricity within the living organism itself.

I shall begin by briefly citing some instances of phenomena which have been referred to the domain of animal electricity, but which do not in reality pertain to it. Thus it was customary, as may be learned from books not of recent date, to cite as a proof of animal electricity the phenomenon developed by stroking with the hand a living cat, or in taking off silk stockings in dry weather. These are effects of electricity developed by rubbing, and may be equally obtained by rubbing with the hand a muff made of a cat's fur. Those also were called currents of animal electricity which resulted from touching with the two ends of the galvanometer the tongue and the forehead when wet with perspiration, or from introducing these ends into the liver and stomach of a living animal. Currents indeed arise, but they are of the same nature with those which we obtain by dipping the extremities, one in a solution of potassa, the other in sulphuric or nitric acid, thus bringing the two liquids into communication. In this experi ment a piece of cloth is immersed in the acid, another piece in the alkali, the two pieces are placed in contact, the circuit closed by the extremities of the galvanometer, and we have a direct current from the alkaline to the acid cloth. Now the sweat is an acid, as is also the gastric juice of the stomach, the saliva and bile have an alkaline reaction, and hence there are direct currents in the animal from the alkaline to the acid liquids. Bellingeri, a distinguished Turinese physiologist, in a memoir on the electricity of animal liquids, thought that he had discovered electro-physiological phenomena, properly so called. He used to operate with a voltaic pair of plates, sometimes on the arterial blood, sometimes on the venous, and again on the urine or saliva. These phenomena, rightly considered, are, and indeed cannot be other than, electro-chemical, and the differences, whatever they may be, depend on the chemical composition of those liquids and their different conductibility. It has been also said that the electric current being passed into albumen, or white of egg, produced organization. The fact is that albumen is coagulated around the electrodes, because these and the liquid grow warm from the passage of the current, and because the acid and alkali produced by the electrization cause the albumen to coagulate.

I have multiplied these examples, because no doubt should be permitted to remain, especially in the beginning of this course, respecting the distinction which it is requisite to make between electro-physiological phenomena really pertaining to the living organism, and the electrical effects which are produced in animal or vegetable tissues whether alive or dead, and which are due to known physical or chemical actions. Of this kind are certain other effects of electricity on vegetation in which there has been a more persistent disposition to see a relation between electricity and the living organism.

You are, perhaps, not ignorant that there is an aquatic plant, the chara, whose stalk, observed with the microscope, presents a singular phenomenon. It is divided into compartments, in each of which are seen regularly moving or circulating globules or cellules. These movements, the cause of which is unknown, stop when an electric discharge passes through the stalk, and all circulation finally ceases if the discharge is very strong. We must infer that the discharge acts either by mechanically destroying the structure of the plant, or coagulating the liquid which it contains, or by altering the chemical composition, effects which all suffice to explain the observed results.

An eminent physicist of Turin, Vassalli-Eandi, made a series of ingenious experiments to show that seeds exposed frequently in the focus of an electric machine germinate before others not thus electrified. I know not whether there has been any verification of this fact, but it might be accounted for by attributing the effect to the oxygen, or rather to the ozone, which is known to favor germination; and ozone is formed in contact with the electrical focus. I have here the usual ozonemetric paper covered with iodine of potassa and baked starch, and it will be seen that, under the electric discharge, the paper becomes blue, an effect which is due to the ozone.

ELECTRO PHYSIOLOGY.

Your attention is finally called to what has taken place from causing an electrical current to pass for several days into a large piece of flannel moistened with a slightly salt solution, and on which were scattered seeds of the mustard, millet, and vetch. You observe that, in contact with the negative electrode, the seeds have already germinated and have even the small leaves, but this is not the case with those in contact with the positive electrode. Neither is this phenomenon an electro-physiological one, properly speaking, but a secondary effect of electricity. At the negative electrode is developed the alkali, and at the positive the acid, as is shown by the reactive paper. Now, in the slightly alkaline solution seeds germinate more readily than in pure water, and in the acid solution they do not germinate at all. In germination the diastasis should act upon the fecula in order to render it soluble, and convert it into dextrine and glucose, and this does not take place in presence of the acid, or, rather, takes place better in presence of a slightly alkaline solution. This is also shown by experiments in which, independently of a current, I have placed the same seeds, some in contact with slightly alkaline solutions, and some in contact with acid solutions. The seeds have germinated in the first case and not in the second. Let us come now to true electro-physiological phenomena; that is, to the contractions which are excited in an animal, either living or recently dead, by the passage of electricity. It is thus that we designate the electric shock; the pain and involuntary muscular contraction which occur when we touch the two armatures of a charged Leyden jar, or the poles of a battery formed of several pairs, or the extremities of a spiral of an apparatus of induction. Before proceeding it is, perhaps, not superfluous to observe, that the property which the muscles possess of contracting is inherent in their nature, and that this property be is chiefly manifested through the excitation of the nervous fibres distributed in the muscle. There is no muscle entirely destitute of nerves, by which may demonstrated the truth first announced by Haller, that the muscles possess contractility. This truth is conformable to all physiological analogies, and the experiments are various by which it is established.

I have here two prepared frogs: one of them was poisoned with curare, the other killed while the first was dying. If I touch the nerves of the poisoned frog with the poles of a battery no muscular contraction is excited, but on operating with the current on the muscles contraction is manifested. In the other frog contraction takes place in both modes. The muscle then will contract under direct irritation when the nerves have lost their excitability. Lately a young French physiologist, M. Faivre, has shown that several hours after death, and when the nerves have lost all excitability, the muscular irritability is augmented. We have here, then, two distinct things: the irritability of the muscles, and the capacity of the nerves to awaken that irritability.

I will remind you, further, that from one of the finest experiments of physiology, for which we are indebted to Charles Bell, we know that roots of nerves issue from the spinal medulla, which, before uniting to form the so-called mixed nerves distributed in the muscles and in all parts of the body, have distinct properties. If the anterior roots be irritated, very strong muscular contractions occur, and nothing else; if the posterior roots, the animal utters cries and gives signs of pain, but there is no contraction. By irritating the mixed nerves in a living animal we obtain at the same time contractions and signs of pain.

Let us begin by preparing a frog in such a manner as may serve to exhibit contraction with the electric current. For that purpose it is divided in half below the upper members, the skin taken off, the viscera are removed from the lower section, and by introducing the scissors under the spinal or lumbar nerves a part of the pelvis is separated, by which means the animal is reduced to a portion of the spine, the lumbar plexus, and the two hinder legs. This is called the frog prepared after the manner of Galvani. I take a small pair of plates of Volta, formed with a wire of zinc and one of copper or platina twisted or