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In a large number of cases； as with the salivary and lacrymal glands； intestinal canal； &c。； the power of attention seems to rest； either chiefly； or as some physiologists think； exclusively； on the vaso…motor system being affected in such a manner that more blood is allowed to flow into the capillaries of the part in question。 This increased action of the capillaries may in some cases be combined with the simultaneously increased activity of the sensorium。
The manner in which the mind affects the vasomotor system may be conceived in the following manner。 When we actually taste sour fruit； an impression is sent through the gustatory nerves to a certain part of the sensorium； this transmits nerve…force to the vasomotor centre； which consequently allows the muscular coats of the small arteries that permeate the salivary glands to relax。 Hence more blood flows into these glands； and they secrete a copious supply of saliva。 Now it does not seem an improbable assumption； that； when we reflect intently on a sensation； the same part of the sensorium； or a closely connected part of it； is brought into a state of activity； in the same manner as when we actually perceive the sensation。 If so； the same cells in the brain will be excited； though； perhaps； in a less degree； by vividly thinking about a sour taste； as by perceiving it； and they will transmit in the one case； as in the other； nerve…force to the vaso…motor centre with the same results。
To give another； and； in some respects； more appropriate illustration。 If a man stands before a hot fire； his face reddens。 This appears to be due； as Mr。 Michael Foster informs me； in part to the local action of the heat； and in part to a reflex action from the vaso…motor centres。＇46＇ In this latter case； the heat affects the nerves of the face； these transmit an impression to the sensory cells of the brain； which act on the vaso…motor centre； and this reacts on the small arteries of the face； relaxing them and allowing them to become filled with blood。 Here； again； it seems not improbable that if we were repeatedly to concentrate with great earnestness our attention on the recollection of our heated faces； the same part of the sensorium which gives us the consciousness of actual heat would be in some slight degree stimulated； and would in consequence tend to transmit some nerve…force to the vaso…motor centres； so as to relax the capillaries of the face。 Now as men during endless generations have had their attention often and earnestly directed to their personal appearance； and especially to their faces； any incipient tendency in the facial capillaries to be thus affected will have become in the course of time greatly strengthened through the principles just referred to； namely； nerve…force passing readily along accustomed channels； and inherited habit。 Thus； as it appears to me； a plausible explanation is afforded of the leading phenomena connected with the act of blushing。
_Recapitulation_。Men and women； and especially the young； have always valued； in a high degree； their personal appearance； and have likewise regarded the appearance of others。 The face has been the chief object of attention； though； when man aboriginally went naked； the whole surface of his body would have been attended to。 Our self…attention is excited almost exclusively by the opinion of others； for no person living in absolute solitude would care about his appearance。 Every one feels blame more acutely than praise。 Now； whenever we know； or suppose； that others are depreciating our personal appearance； our attention is strongly drawn towards ourselves； more especially to our faces。 The probable effect of this will be； as has just been explained； to excite into activity that part of the sensorium； which receives the sensory nerves of the face； and this will react through the vaso…motor system on the facial capillaries。 By frequent reiteration during numberless generations； the process will have become so habitual； in association with the belief that others are thinking of us； that even a suspicion of their depreciation suffices to relax the capillaries； without any conscious thought about our faces。 With some sensitive persons it is enough even to notice their dress to produce the same effect。 Through the force； also； of association and inheritance our capillaries are relaxed； whenever we know； or imagine； that any one is blaming； though in silence； our actions； thoughts； or character； and； again； when we are highly praised。
＇46＇ See； also； Mr。 Michael Foster； on the action of the vaso…motor system； in his interesting Lecture before the royal Institution； as translated in the ‘Revue des Cours Scientifiques；' Sept。 25； 1869； p。 683。
On this hypothesis we can understand how it is that the face blushes much more than any other part of the body； though the whole surface is somewhat affected； more especially with the races which still go nearly naked。 It is not at all surprising that the dark…coloured races should blush； though no change of colour is visible in their skins。 From the principle of inheritance it is not surprising that persons born blind should blush。 We can understand why the young are much more affected than the old； and women more than men； and why the opposite sexes especially excite each other's blushes。 It becomes obvious why personal remarks should be particularly liable to cause blushing； and why the most powerful of all the causes is shyness； for shyness relates to the presence and opinion of others； and the shy are always more or less self…conscious。 With respect to real shame from moral delinquencies； we can perceive why it is not guilt； but the thought that others think us guilty； which raises a blush。 A man reflecting on a crime committed in solitude； and stung by his conscience； does not blush； yet he will blush under the vivid recollection of a detected fault； or of one committed in the presence of others； the degree of blushing being closely related to the feeling of regard for those who have detected； witnessed； or suspected his fault。
Breaches of conventional rules of conduct； if they are rigidly insisted on by our equals or superiors； often cause more intense blushes even than a detected crime； and an act which is really criminal； if not blamed by our equals； hardly raises a tinge of colour on our cheeks。 Modesty from humility； or from an indelicacy； excites a vivid blush； as both relate to the judgment or fixed customs of others。
From the intimate sympathy which exists between the capillary circulation of the surface of the head and of the brain； whenever there is intense blushing； there will be some； and often great； confusion of mind。 This is frequently accompanied by awkward movements； and sometimes by the involuntary twitching of certain muscles。
As blushing； according to this hypothesis； is an indirect result of attention； originally directed to our personal appearance； that is to the surface of the body； and more especially to the face； we can understand the meaning of the gestures which accompany blushing throughout the world。 These consist in hiding the face； or turning it towards the ground； or to one side。 The eyes are generally averted or are restless； for to look at the man who causes us to feel shame or shyness； immediately brings home in an intolerable manner the consciousness that his gaze is directed on us。 Through the principle of associated habit； the same movements of the face and eyes are practised； and can； indeed； hardly be avoided； whenever we know or believe that； others are blaming； or too strongly praising； our moral conduct。 CHAPTER XIV。
CONCLUDING REMARKS AND SUMMARY。
The three leading principles which have determined the chief movements of expressionTheir inheritanceOn the part which the will and intention have played in the acquirement of various expressions The instinctive recognition of expressionThe bearing of our subject on the specific unity of the races of manOn the successive acquirement of various expressions by the progenitors of man The importance of expressionConclusion。
I HAVE now described； to the best of my ability； the chief expressive actions in man； and in some few of the lower animals。 I have also attempted to explain the origin or development of these actions through the three principles given in the first chapter。 The first of these principles is； that movements which are serviceable in gratifying some desire； or in relieving some sensation； if often repeated； become so habitual that they are performed； whether or not of any service； whenever the same desire or sensation is felt； even in a very weak degree。
Our second principle is that of antithesis。 The habit of voluntarily performing opposite movements under opposite impulses has become firmly established in us by the practice of our whole lives。 Hence； if certain actions have been regularly performed； in accordance with our first principle； under a certain frame of mind； there will be a strong and involuntary tendency to the performance of directly opposite actions； whether or not these are of any use； under the excitement of an opposite frame of mind。
Our third principle is the direct action of the excited nervous system on the body； independ