CHAP. VI. WEEPING. 159 act downwards with unusual force in expelling the con- tents of the intestinal canal. The greatest exertion of the muscles of the body, if those of the chest are not brought into strong action in expelling or compressing the air within the lungs, does not lead to the contraction of the muscles round the eyes. I have observed my sons using great force in gym- nastic exercises, as in repeatedly raising their suspended bodies by their arms alone, and in lifting heavy weights from the ground, but there was hardly any trace of con- traction in the muscles round the eyes. As the contraction of these muscles for the protection of the e3~es during violent expiration is indirectly, as we shall hereafter see, a fundamental element in several of our most important expressions, I was extremely anxious to ascertain how far Sir C. BelPs view could be substantiated. Professor Bonders, of Utrecht,14 well tnown as one of the highest authorities in Europe on •vision and on the structure of the eye, has most Mndly undertaken for me this investigation with the aid of the many ingenious mechanisms of modern science, and has published the results.15 He shows that during violent expiration the external, the infra-ocular, and the retro- ocular vessels of the eye are all affected in two ways, namely by the increased pressure of the blood in the arteries, and by the return of the blood in the veins 14 I am greatly indebted to Mr. Bowman for having- introduced me to Prof. Bonders, and for his aid in per- suading: this great physiologist to undertake the inves- tigation of the present subject. I am likewise much in- debted to Mr. Bowman for having- given me, with the •utmost kindness, information on many points. 15 This memoir first appeared in the * Nederlandsch Archief voor Genees en Natuurkunde/ Deel 5, 1870. It has been translated by Dr. W. D. Moore, under the title of " On the Action of the Eyelids in determination of Blood from expiratory effort," in * Archives of Medicine,* edited by Dr. L. S. Beale, 1870, vol. v. p. 20.