The relation thus shewn to subsist between the stomach and the brain, enables us in some measure to understand the influence which strong mental emotions and earnest intellectual occupation exert over the appetite. A man in perfect health, sitting down to table with an excellent appetite, receives a letter announcing an unexpected calamity, and instantly turns away with loathing from the food which, a moment before, he was prepared to eat with relish; while another, who, under the fear of some misfortune, comes to table indifferent about food, will eat with great zest on his “mind being relieved,” as the phrase goes, by the receipt of pleasing intelligence. Excessive and absorbing emotion, even of a joyful kind, has the same effect. Captain Back tells us in the interesting narrative of his last journey, that when he first heard of Captain Ross’s return, “the thought of so wonderful a preservation overpowered, for a time, the common occurrences of life. _We had but just sat down to breakfast, but our appetite was gone_, and the day passed in a feverish state of excitement,” (P. 245). In such cases, no one will imagine that the external cause destroys appetite otherwise than through the medium of the brain. Occasionally, indeed, the aversion to food amounts to a feeling of loathing and disgust, and even induces sickness and vomiting,--a result which depends so entirely on the state of the brain, that it is often excited by mechanical injuries of that organ. The analogy between the external senses and the appetite is in various respects very close. If we are wrapt in study, or intent on any scheme, we become insensible to impressions made on the ear or eye. A clock may strike, or a person enter the room, without our being aware of either event. The same is the case with the desire for food. If the mind is deeply engaged, the wants of the system are unperceived and unattended to--as was well exemplified in the instance of Sir Isaac Newton, who, from seeing the bones of a chicken lying before him, fancied that he had already dined, whereas, in reality, he had eaten nothing for many hours. Herodotus ascribes so much efficacy to mental occupation in deadening the sense of hunger, that he speaks of the inhabitants of Lydia having successfully had recourse to gaming as a partial substitute for food, during a famine of many years continuance. In this account there is, of course, gross exaggeration; but it illustrates sufficiently well the principle under discussion.