172 EXPRESSION OF SUFFERING: Chap. VI. 



f erred to by Professor Donders and Mr. Bowman, we 

 have seen that some weeks after the eye lias 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 spasmodi- 

 cally and therefore with much greater force than can 

 be done voluntarily, should be sufficient to cause by re- 

 flex action the secretion of tears in the many cases in 

 which this occurs during violent expiratory efforts. 



Another cause may come conjointly into play. We 

 have seen that the internal parts of the eye, under cer- 

 tain 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 glands — the ef- 

 fects 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 gen- 

 erations, whenever they have screamed; and on the prin- 

 ciple 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 



