Nature has accorded to man considerable latitude in fixing the interval within which the demands of appetite must be gratified, and in this provision has obviously had in view the infinite variety of circumstances in which he may be placed in the discharge of his numerous duties. As a general rule, five or six hours should elapse between one meal and another--longer if the mode of life be indolent, shorter if very active. Digestion occupies from three to five hours, according to the nature of the meal and circumstances of the case, and _the stomach requires an interval of rest after the process is finished, to enable it to recover its tone, before it can again enter upon the vigorous performance of its function_. Appetite, accordingly, does not begin to shew itself till some time after the stomach has been empty, and if food be taken before it has recovered its tone, the secretion of gastric juice and the contraction of its muscular fibres are alike imperfect, and digestion consequently becomes impaired. If, again, food be taken before the digestion of the preceding meal be completed, the result will be still worse; because the whole of the gastric juice which the stomach can secrete being already engaged in the solution of the first meal, the one subsequently taken necessarily remains unsupplied, and consequently liable to undergo the same chemical change--fermentation--which would occur in it if exposed _out of_ the _stomach_ to an equal degree of heat and moisture. And, therefore, Dr Kitchener, in alluding to the advantages arising from giving the stomach an occasional rest, truly and forcibly remarks, that “unless the constitution is so confoundedly debilitated that the circulation will not run alone, abstinence is the easiest--cheapest--and best cure for the disorders which arise from indigestion or intemperance.” (P. 160.) In these cases, indeed, abstinence is to the exhausted stomach what repose is to the wearied muscles, and hence the benefits resulting from it. The interval between each meal ought to be longer or shorter in proportion to the quantity eaten, and to the more or less active habits of the individual; and it would be absurd to fix the same standard for all. A strong labouring man, whose system is subjected to great waste from being engaged all day in hard work, will require not only more frequent but more copious meals than an indolent and sedentary man; and those who eat very little will require to eat at shorter intervals than those whose meals are heavy. An invalid on restricted diet may thus require to eat every four hours, where formerly, with a more copious diet, once in six hours was sufficient. Some indeed are so constituted as to require only one or two abundant meals in twenty-four hours.