106. See also his paper in the `Philosophical Transactions,' 1822, p. 284, ibid. 1823, pp. 166 and 289. Also `The Nervous System of the Human Body,' 3rd edit. 1836, p. 175.
Not only are the muscles round the eyes strongly contracted, as Sir C. Bell states and as I have often observed, during screaming, loud laughter, coughing, and sneezing, but during several other analogous actions. A man contracts these muscles when he violently blows his nose. I asked one of my boys to shout as loudly as he possibly could, and as soon as he began, he firmly contracted his orbicular muscles; I observed this repeatedly, and on asking him why he had every time so firmly closed his eyes, I found that he was quite unaware of the fact: he had acted instinctively or unconsciously.
It is not necessary, in order to lead to the contraction of these muscles, that air should actually be expelled from the chest; it suffices that the muscles of the chest and abdomen should contract with great force, whilst by the closure of the glottis no air escapes. In violent vomiting or retching the diaphragm is made to descend by the chest being filled with air; it is then held in this position by the closure of the glottis, "as well as by the contraction of its own fibres."[13] The abdominal muscles now contract strongly upon the stomach, its proper muscles likewise contracting, and the contents are thus ejected. During each effort of vomiting "the head becomes greatly congested, so that the features are red and swollen, and the large veins of the face and temples visibly dilated." At the same time, as I know from observation, the muscles round the eyes are strongly contracted. This is likewise the case when the abdominal muscles act downwards with unusual force in expelling the contents of the intestinal canal.
[13] See Dr. Brinton's account of the act of vomiting, in Todd's Cyclop. of Anatomy and Physiology, 1859, vol. v. Supplement, p. 318.
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 gymnastic 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 contraction in the muscles round the eyes.
As the contraction of these muscles for the protection of the eyes 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. Bell's view could be substantiated. Professor Donders, of Utrecht,[14] well known as one of the highest authorities in Europe on vision and on the structure of the eye, has most kindly 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 intra-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 being impeded. It is, therefore, certain that both the arteries and the veins of the eye are more or less distended during violent expiration. The evidence in detail may be found in Professor Donders' valuable memoir. We see the effects on the veins of the head, in their prominence, and in the purple colour of the face of a man who coughs violently from being half choked. I may mention, on the same authority, that the whole eye certainly advances a little during each violent expiration. This is due to the dilatation of the retro-ocular vessels, and might have been expected from the intimate connection of the eye and brain; the brain being known to rise and fall with each respiration, when a portion of the skull has been removed; and as may be seen along the unclosed sutures of infants' heads. This also, I presume, is the reason that the eyes of a strangled man appear as if they were starting from their sockets.