or giving them a stimulus from without. This partial dependence of stomachic vigour upon a derived power from the cerebral mass is well attested by the tendency of an overworked brain to bring on disordered digestion-an effect that does not seem to arise so readily in other parts, as the muscles or the lungs. On this point, however, we must make allowance for differences of temperament. The stomachic sensibility will be found very unequal in different individuals, just as we find inequalities in the feeling of music, or any other 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. They are not so violent as lacerations, burns, and broken bones, nor so intense as cramps, nor so fearfully oppressive as suffocation, but for the moment they are sharp and agonizing. 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, intestines, liver, &c., have each their various modes of distemper. 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

Wagner states (Elements of Physiology, § 362), that 'Increased movements of the intestines have been observed when the corpora quadrigemina have been irritated.'

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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 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 have returned; the evil then seems to have neither a local habitation nor a name.

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

Feelings of Electrical States.

19. 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 life. 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 disorganising 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

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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 continuing 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 agonising. 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 trying both common and voltaic electricity, for the purpose, Faraday's invention has been adopted in preference to either.

20. 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 general 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.

*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 always in proportion to the degree of cold.

SUBSTANCES ACTING ON THE SENSE OF TASTE. 147

21. 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 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.*

The action of the human hand and the stare of the eye are employed in the process of mesmerism, which has now come to be used as a source of sensation and a cure of disease. Being a soporific influence there is in the action. also the included quality of soothing the nervous system under pain and irritation, and thus of inducing again the more healthy texture of the nervous substance.

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 first reception of the nutritive material.

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 a 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 are distinguished from one another by means of this property.

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 writings generally.

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.

It is a curious fact, that the chemical combination M2 O3, or two atoms of a metal with three of oxygen (termed also 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. Caramel, the bitter of toast and water, of chicory, and of burnt malt in porter, is singularly enough closely allied in composition to sugar. It is the black matter formed by heating sugar to about 400°, and has the same chemical formula as waterless cane sugar.

There is a certain class of vegetable compounds, neutral bodies, which are at present characterised as the bitter and

* In all the bodies where this bitter is produced, the effect is due to the same cause, namely, the heating of a portion of the sugar contained in the substance. Hence the sweet roots, such as beet and chicory, are ready to yield it. The value of chicory, when mixed with coffee, depends on the production of caramel by the process of roasting.