CHAP. XII. ASTONISHMENT. $83 "be accounted for by mucus accumulating within the tube, and the consequent exclusion of air. We may therefore infer that the mouth is not kept open under the sense of astonishment for the sake of hearing sounds more distinctly; notwithstanding that most deaf people keep their mouths open. Every sudden emotion, including astonishment, quickens the action of the heart, and with it the respira- tion. Xow we can "breathe, as Gratiolet remarks 7 and as appears to me to be the case, much more quietly through the open mouth than through the nostrils. Therefore, when we wish to listen Intently to any sound, we either stop breathing, or breathe as quietly as possible, by open- ing our mouths,, at the same time keeping our bodies motionless. One of my sons was awakened in the night by a noise under circumstances which naturally led to great care, and after a few minutes he perceived that his mouth was widely open. He then became conscious that he had opened it for the sake of breathing as quietly as possible. Tliis view receives support from the reversed case which occurs with dogs. A dog when panting after exercise, or on a hot day., breathes loudly; but if his at- tention be suddenly aroxised, he instantly pricks his ears to listen, shuts his mouth, and breathes quietly, as he is enabled to do, through his nostrils. "When the attention Is concentrated for a length of time with fixed earnestness on any object or subject, all the organs of the body are forgotten and neglected;s and as the nervous energy of each individual is limited in amount, little is transmitted to any part of the system, excepting that -which is at the time brought into ener- getic action. Therefore many of the muscles tend to 7 ' De la Physionomie,' 1865, p. 234. 8 See, on this subject, Gratiolet, ibid. p. 254.