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s in connection with the retina； to the sensory nerve…cells of the nose； causing it to tickle； and from these； to the cells which command the various respiratory muscles （the orbiculars included） which expel the air in so peculiar a manner that it rushes through the nostrils alone。
To return to our point： why are tears secreted during a screaming…fit or other violent expiratory efforts？ As a slight blow on the eyelids causes a copious secretion of tears； it is at least possible that the spasmodic contraction of the eyelids； by pressing strongly on the eyeball； should in a similar manner cause some secretion。 This seems possible； although the voluntary contraction of the same muscles does not produce any such effect。 We know that a man cannot voluntarily sneeze or cough with nearly the same force as he does automatically； and so it is with the contraction of the orbicular muscles： Sir C。 Bell experimented on them； and found that by suddenly and forcibly closing the eyelids in the dark； sparks of light are seen； like those caused by tapping the eyelids with the fingers； 〃but in sneezing the compression is both more rapid and more forcible； and the sparks are more brilliant。〃 That these sparks are due to the contraction of the eyelids is clear； because if they 〃are held open during the act of sneezing； no sensation of light will be experienced。〃 In the peculiar cases referred to by Professor Donders and Mr。 Bowman； we have seen that some weeks after the eye has been very slightly injured； spasmodic contractions of the eyelids ensue； and these are accompanied by a profuse flow of tears。 In the act of yawning； the tears are apparently due solely to the spasmodic contraction of the muscles round the eyes。 Notwithstanding these latter cases； it seems hardly credible that the pressure of the eyelids on the surface of the eye； although effected spasmodically and therefore with much greater force than can be done voluntarily； should be sufficient to cause by reflex action the secretion of tears in the many cases in which this occurs during violent expiratory efforts。
＇23＇ See； on these several points； Prof。 Donders ‘On the Anomalies of Accommodation and Refraction of the Eye；' 1864； p。 573。
Another cause may come conjointly into play。 We have seen that the internal parts of the eye； under certain conditions act in a reflex manner on the lacrymal glands。 We know that during violent expiratory efforts the pressure of the arterial blood within the vessels of the eye is increased； and that the return of the venous blood is impeded。 It seems； therefore； not improbable that the distension of the ocular vessels； thus induced； might act by reflection on the lacrymal glandsthe effects due to the spasmodic pressure of the eyelids on the surface of the eye being thus increased。
In considering how far this view is probable； we should bear in mind that the eyes of infants have been acted on in this double manner during numberless generations； whenever they have screamed； and on the principle of nerve…force readily passing along accustomed channels； even a moderate compression of the eyeballs and a moderate distension of the ocular vessels would ultimately come； through habit； to act on the glands。 We have an analogous case in the orbicular muscles being almost always contracted in some slight degree； even during a gentle crying…fit； when there can be no distension of the vessels and no uncomfortable sensation excited within the eyes。
Moreover； when complex actions or movements have long been performed in strict association together； and these are from any cause at first voluntarily and afterwards habitually checked； then if the proper exciting conditions occur； any part of the action or movement which is least under the control of the will； will often still be involuntarily performed。 The secretion by a gland is remarkably free from the influence of the will； therefore； when with the advancing age of the individual； or with the advancing culture of the race； the habit of crying out or screaming is restrained； and there is consequently no distension of the blood…vessels of the eye； it may nevertheless well happen that tears should still be secreted。 We may see； as lately remarked； the muscles round the eyes of a person who reads a pathetic story； twitching or trembling in so slight a degree as hardly to be detected。 In this case there has been no screaming and no distension of the blood…vessels； yet through habit certain nerve…cells send a small amount of nerve…force to the cells commanding the muscles round the eyes； and they likewise send some to the cells commanding the lacrymal glands； for the eyes often become at the same time just moistened with tears。 If the twitching of the muscles round the eyes and the secretion of tears had been completely prevented； nevertheless it is almost certain that there would have been some tendency to transmit nerve…force in these same directions； and as the lacrymal glands are remarkably free from the control of the will； they would be eminently liable still to act； thus betraying； though there were no other outward signs； the pathetic thoughts which were passing through the person's mind。
As a further illustration of the view here advanced； I may remark that if； during an early period of life； when habits of all kinds are readily established； our infants； when pleased； had been accustomed to utter loud peals of laughter （during which the vessels of their eyes are distended） as often and as continuously as they have yielded when distressed to screaming…fits； then it is probable that in after life tears would have been as copiously and as regularly secreted under the one state of mind as under the other。 Gentle laughter； or a smile； or even a pleasing thought； would have sufficed to cause a moderate secretion of tears。 There does indeed exist an evident tendency in this direction； as will be seen in a future chapter； when we treat of the tender feelings。 With the Sandwich Islanders； according to Freycinet；＇24＇ tears are actually recognized as a sign of happiness； but we should require better evidence on this head than that of a passing voyager。 So again if our infants； during many generations； and each of them during several years； had almost daily suffered from prolonged choking…fits； during which the vessels of the eye are distended and tears copiously secreted； then it is probable； such is the force of associated habit； that during after life the mere thought of a choke； without any distress of mind； would have sufficed to bring tears into our eyes。
To sum up this chapter； weeping is probably the result of some such chain of events as follows。 Children； when wanting food or suffering in any way； cry out loudly； like the young of most other animals； partly as a call to their parents for aid； and partly from any great exertion serving relief。 Prolonged screaming inevitably leads to the gorging of the blood…vessels of the eye； and this will have led； at first consciously and at last habitually； to the contraction of the muscles round the eyes in order to protect them。 At the same time the spasmodic pressure on the surface of the eye； and the distension of the vessels within the eye； withou