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Perhaps this is due to the fact that development means, among other things, multiplying ways of reacting to what is superficially the same situation. Man sees a greater number of possible reactions-more ways of behaving-with reference to external situations than do the lower animals. Primitive man, also, was consistent until he learned inconsistency from contact with his civilized teacher. The larger number of possible responses are confusing. Putting them in order requires the organization of information and moral principles, as well as insight into the effect of acts; and thinking in terms of cause and effect is a comparatively new instrument of behavior.

The man of good intentions, however, who yields to moral weakness has moments of keen remorse. But the effect is momentary. He repents and sins again. Some people have the repentance habit. They gain a certain solace and even joy from the excitement. It is a sort of emotional debauchery in which they indulge periodically, just as others drown their sorrow in drink. This is one of the ways in which the emotions ooze out ineffectually instead of producing action which is the phylogenetic justification for their existence. In time, inaction, with such people, becomes a fixed mode of behavior. They are continually making resolutions which are never carried

out.

This feeling of remorse easily leads to the self-deception to which, as we have said, man is prone. He is much more naïve in this than are those who observe him. He does not know that he is practising self-deception though he may have observed this trait in others. This, again, is human-seeing quite clearly in acquaintances what one does not discover in oneself, though it may be patent to all the rest of the world. It illustrates a certain human blindness.

Finally, there should be a selection of the self to which we yield submission. "Not that I would not, if I could,"

says James, "be both handsome and fat and well dressed, and a great athlete, and make a million a year, be a wit, a bon vivant, and a lady-killer, as well as a philosopher; a philanthropist, statesman, warrior, and African explorer, as well as a 'tone-poet' and saint. But the thing is impossible. The millionaire's work would run counter to the saint's; the bon vivant and the philanthropist would trip each other up; the philosopher and the lady-killer could not well keep house in the same tenement of clay." One or the other will finally dominate. The question is, Which?

CHAPTER X

THE PSYCHOLOGY OF DIGESTION

"It looks so good that it makes my mouth water" is a common saying; and it is not merely a figure of speech. The mouth actually does water at the sight of appetizing food. That is, the flow of saliva begins. Now, since the food has not been tasted the cause of this flow must be altogether different from that which stimulates secretion when food is actually eaten. Evidently, the mind is at work here, with its expectation of approaching pleasure; and this anticipation is one of the psychical contributions to digestion. Its effect, in the feeling of the mouth when appetizing food is offered, is a matter of common experience. It is not so generally known, however, that visions of pleasant eating also make the stomach "water."

As long ago as 1852 two investigators' noticed that the sight and smell of food started gastric secretion in the stomach of a hungry dog, and twenty-six years later Richet reported2 evidence of a generous flow of gastric juice in one of his patients when such substances as sugar or lemonjuice were chewed or tasted, though the act of swallowing could not be completed on account of a closed œsophagus. But the importance of these observations was not understood at the time, and the investigations were unproductive. More recently, however, a Russian physiologist, Pavlov, repeated the experiments on dogs, under improved conditions, and demonstrated the significance for digestion of the psychical factor, desire or appetite.

1 F. Bidder and C. Schmidt, Die Verdauungssäfte und der Stoffwechsel, Leipzig, 1852.

2 Journal de l'Anatomie et de la Physiologie, vol. 14, p. 170.

But let us begin with the first stage of digestion, namely, with the saliva, and see what this mental co-operation means. Of course when food, and especially dry food, is put into the mouth saliva begins to flow. The advantage of this is to moisten the food and render easier the act of swallowing. Animals deprived of the parotid saliva swallow dry food only with the greatest difficulty. In addition, the saliva dissolves the soluble constituents of food, making them perceptible to the nerves of taste, and, in certain articles of diet, it starts the digestive process. Now Pavlov has shown experimentally that it is not necessary for food to be put into the mouth to excite the salivary reflex. All that is needed with a hungry dog is to direct his attention to the food. Then the saliva begins to flow. As might be expected, the success of the experiment depends upon the anticipation elicited by the sight of what is offered. If the animal has found from past experience that it tastes good, the glands begin at once to pour out their secretion abundantly. On the other hand, if previous experience has shown that the substance offered will not taste good, no saliva is secreted. "In the course of our experiments," says Pavlov,1 "it appeared that all the phenomena of adaptation which we saw in the salivary glands under physiological conditions, such, for instance, as the introduction of the stimulating substances into the buccal cavity, reappeared in exactly the same manner under the influence of psychological conditions-that is to say, when we merely drew the animal's attention to the substances in question. Thus, when we pretended to throw pebbles into the dog's mouth, or to cast in sand, or to pour in something disagreeable, or, finally, when we offered it this or that kind of food, a secretion either immediately appeared or it did not appear, in accordance with the properties of the substance which we had previously seen

1 The Work of the Digestive Glands, translated by W. H. Thompson, 193, p. 152.

to regulate the quantity and nature of the juice when physiologically excited to flow." In other words, expectation of a pleasant taste plays an important rôle in promoting the flow of saliva and, consequently, in furthering all of the phases of digestion with which saliva is concerned.

But anticipation reaches far beyond the sight or smell of pleasant food. The food itself need not be present. Anything that is regularly connected with it at an enjoyable meal will be sufficient to stimulate the reflex. Whatever has been associated with the substances that physiologically excite the salivary secretion may arouse it psychologically. The attendant who feeds the animals, his footsteps, taking the dog into the room where he is wont to be fed, the vessel usually containing the food, and the furniture of the room, any one of these will be sufficient to produce the flow. Curiously enough, substances which stimulate the reflex in a purely mechanical way, irrespective of enjoyment, have the same effect-the sight of the bottle containing the acid that starts the secretion mechanically, for example. If the acid is dark, then water in the bottle of the same color as the acid will produce a like effect.1 Since it is the color that exerts the influence, dogs, according to Pavlov, distinguish certain colors. If an illuminated circle be shown with food the circle alone will finally excite the reflex. Since an illuminated quadrilateral does not have this effect, dogs appear to distinguish between these figures. "If a definite musical note be repeatedly sounded in conjunction with the exhibition of meat-powder, after a time the sound of the note alone is effective. Similarly with the exhibition of a brilliant color." 2 Since a difference of a quarter of a tone produces no result, the dog seems to make this distinction. Indeed,

1 A. Meisl, Journal für Psychologie und Neurologie, vol. 6, p. 192; Wien. kl. Rundschau, vol. 17, p. 375. W. Nicolai, Journal für Psychologie und Neurologie, vol. 10, p. 1.

2 Pavlov, op. cit., p. 85.

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