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. 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 glands—the effects due to the spasmodic pressure of the eyelids on the surface of the eye being thus increased.