sense.

Some persons count the feelings of digestion a very small item among the sources of pleasurable excitement; but I am led to suppose, from the prevailing attention to the choice and preparation of food, that, for the great majority of people, I have not overstated their importance.

On acute stomachic pains, it is not necessary to spend much discussion. They have their character chiefly from the great sensibility of the alimentary surface, which often makes a slight cause of irritation peculiarly keen and intolerable. On the subject of pains and distempers not acute, but connected with want of tone and vigour in the digestive system, or with deranged mucous surface, the pathologist and physician have much to describe. The stomach combines the nourishing and the purifying functions; and hence operates doubly upon the healthy condition of the blood, the general basis of bodily and mental vigour. A well-known form of depression accompanies deficiency in the excreting power of the alimentary canal; so much so, that a forced relief of the loaded organs produces a general exhilaration; the consequence of withdrawing impurity from the blood. But what chiefly interests us is to mark, as a specific mental experience arising out of many forms of alimentary derangement, the depression and ennui spread over the consciousness, at the times when any of these organs are failing to perform their part. This effect is one that, if not intense or acute, is powerful in its amount, and extremely difficult to combat, either by other stimulants, or by the action of the mind recalling or imagining situations of a less gloomy cast. It either resembles or else produces that physical depression of the nervous substance already considered; the likeness holds remarkably in the leading features, as in the distaste for existence while the state lasts, and in the extreme facility of forgetting it when it is gone. In the rational point of view, hardly any sacrifice is too much to prevent the frequent recurrence of this state, but so little hold does it take as a permanent impression, that the reason has very little power in the matter. Any feeling of general depression is easily

forgotten when the animal spirits are restored; the evil then seems to have neither a local habitation nor a name.

We have now described the principal states of feeling that enter into the general conditions called physical Comfort and Discomfort. The most powerful constituent elements of these two opposite modes of existence, are the feelings of the muscular system as regards exercise, and the various classes of organic sensations above enumerated.

Feelings of Electrical States.

23. We shall touch upon only one other class of feelings before passing from this subject, the feelings of Electric and Magnetic agencies. It is very difficult to say anything precise on this class of sensations, but their interest is such that we ought not to pass them unnoticed.

The electric shock from a Leyden jar is perhaps the simplest of all the electric effects; yet we are not able to describe the change that it produces on the tissues affected by it. When very severe it destroys lifc. The stroke of lightning is proved to be of the same nature. The peculiar feeling of this kind of electricity has its main character from the suddenness of the action; the painful effect is described as a shock or a blow. When pretty smart, it leaves an unpleasant impression behind, such as to render us averse to a repetition of the experiment. There can be no doubt of the disorganizing tendency of the influence when at all severe; and the impression is one that remains with us as a thing of dread, like a scald or the blow of a weapon. The Voltaic shock is very different, in consequence of the altered character of the discharge; an incessant current is substituted for an instantaneous shock. Still the painful character remains. The first contact causes a slight blow like the other; then succeeds a feeling of heat, and a creeping sensation of the flesh as if it were unnaturally wrenched or torn, which after a time becomes intolerable. The peculiar distorting sensation is carried to the utmost in Faraday's Magneto-Electric Machine, where the current, instead of con

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tinuing of one character, is changed from negative to positive, and from positive to negative, a great many times every second. The sense of contortion from this machine may be described as agonizing. Feebler discharges of this kind are employed as an electric stimulus in certain diseases. There seems to be a power in electricity to revive the action of torpid nerves; and after experience both of common and of voltaic electricity for the purpose, Faraday's invention has been adopted in preference to either.

24. The electricity of the Atmosphere is believed to be the cause of quite other sensations than the shock of the thunderbolt. In some states, this influence is supposed to kindle a genial glow in the human frame, while in other states, the effect is painful and depressing. Many persons complain of a disturbed irritated condition of body on the eve of a thunder-storm. The highly electrified state of the atmosphere in dry cold is generally considered as bracing; while part of the depression of moist sultry weather is attributed to the absence of electricity.* Much, however, remains to be proved in regard to these popular beliefs. The time of greatest influence on the human sensibility from this class of influences is the eve of an earthquake or volcanic eruption; in which case it is known that the earth's magnetism suffers violent disturbances. On these occasions, feelings of depression amounting to nausea and sickness overtake both men and animals, as if some great stimulus of a supporting kind were suddenly withdrawn.

25. The influence of magnetism has been applied to produce new and artificial sensations in such experiments as those of Baron Reichenbach; but as the same sensations have been caused by crystals, heat, light, chemical activity, and the living hand, they can hardly be assigned specifically to the magnetic action. Reichenbach records two different

* I am informed, as the result of the observations at Kew Observatory (adopted at the instance of the British Association, for observing atmospheric electrical states), that the electricity of the air is usually in proportion to the degree of cold.

classes of feelings arising in his patients, according to the polar direction of the agent; the one cool, refreshing, delightful; the other in all respects the opposite.*

SENSE OF TASTE.

This is a peculiar sense attached to the entrance of the alimentary canal, as an additional help in discriminating what is proper to be taken as food, and an additional source of enjoyment in connexion with the act of eating.

1. The substances used as food are more completely distinguished by the taste than by the digestion. The tastes of bodies are almost as widely different as is their chemical composition; but in order to have taste, a substance must be either liquid or soluble in the mouth.

The bodies acting on the sense of Taste are innumerable. They are found in the mineral, vegetable, and animal kingdoms, and many of them may be discriminated by means of this property.

Of mineral bodies, water and the elements of atmospheric air are remarkable for having no taste. But most other liquids and gases, and a very great proportion of solid substances, if capable of being dissolved by the saliva, have a distinct action on the palate. All acids, all alkalies, and nearly all soluble salts are sapid.

It is remarked that, in salts, the taste is determined more by the base than by the acid. Thus salts of iron have in general the inky taste; salts of magnesia partake more or less of the well known character of Epsom salts. There is also something of a common character in the salts of silver, of soda, of potash, of ammonia.

* I may remark, however, that although Reichenbach's experiments have been performed with an amount of care unknown before in this class of subjects, and rivalling the most approved scientific researches, yet it is still a doubt with many whether these effects be not due to imagination. Mr. Braid's admirable observations on the influence of ideas in producing bodily states, show to what great lengths the power of imagination may go in a peculiar class of temperaments.-(See his criticism on Reichenbach, and his writings generally.)

It is a curious fact, that the chemical combination M2 O3, or two atoms of a metal with three of oxygen (termed sesquioxides) causes sweetness. Alumina is an illustration; for alum is known to be sweet as well as astringent. The oxide of chromium is still sweeter. Glucina is the sweetest of all, and has its name from this quality.

The salt of silver, termed hypo-sulphite, and its combinations with hypo-sulphites of the alkalies, are the sweetest bodies known.

The salts of lime are bitter.

The organic alkalies are all intensely bitter; quinine, morphine, strychnine, are instances. The taste of strychnine is apparent when diluted with water, to the degree of one in a million.

There is a certain class of vegetable compounds, neutral bodies, which are at present characterized as the bitter and extractive principles of plants. I quote a few examples from the list given in GREGORY'S Organic Chemistry, p. 457.

Gentianine, from Gentiana lutea, forms yellow needles, very bitter. Absinthine, from Artemisia absintheum, or wormwood, is a semi-crystalline mass, very bitter, soluble in alcohol. Tanacetine, from tanacetum vulgare, is very similar to it. Syringine is the bitter principle of the lilac, syringa vulgaris. Colocynthine, the active principle of colocynth, is amorphous, intensely bitter and purgative.

Quassine is a yellow, crystalline, and very bitter substance, from the wood of quassia amara. Lupuline is the bitter principle of hops. Liminine, or Limine, is a bitter crystalline matter, found in the seeds of oranges, lemons, &c.

With regard to vegetable and animal substances in general, Gmelin remarks:-Some organic compounds, as gum, starch, woody fibre, white of egg, &c., have no taste; others have a sour taste (most acids); or a rough taste (tannin); or sweet (sugar, glycerine, glycocol); or bitter (bitter principles, narcotic substances, and many acrid substances, also many resins); or acrid (acrid oils and camphors,