They are these: 1. The _blood_ requires exercise: 2. The great central organ of the _stomach_ requires adaptation of diet: 3. The _nervous system_ requires regularity of sleep. In those three functions of sleep, diet, exercise, is contained the whole economy of health. All three of course act and react upon each other: and all three are wofully deranged by a London life--above all, by a parliamentary life. As to the first point, it is probable that any torpor, or even _lentor_ in the blood, such as scarcely expresses itself sensibly through the pulse, renders that fluid less able to resist the first actions of disease. As to the second, a more complex subject, luckily we benefit not by our own brief experience exclusively; every man benefits practically by the traditional experience of ages, which constitutes the culinary experience in every land and every household. The inheritance of knowledge, which every generation receives, as to the salubrity of this or that article of diet, operates continually in preventing dishes from being brought to table. Each man's separate experience does something to arm him against the temptation when it is offered; and again, the traditional experience far oftener intercepts the temptation. As to the third head, _sleep_, this of all is the most immediately fitted by nature to the relief of the brain and its exquisite machinery of nerves:--it is the function of health most attended to in our navy; and of all it is the one most painfully ravaged by a London life. Thus it would appear, that the three great laws of health, viz., _motion_, _rest_, and _temperance_, (by a more adequate expression, _adaptation to the organ_,) are, in a certain gross way, taught to every man by his personal experience. The difficulty is--as in so many other cases--not for the understanding, but for the will--not to know, but to execute. Now here steps in Casuistry with two tremendous suggestions, sufficient to alarm any thoughtful man, and rouse him more effectually to the performance of his duty. First, that under the same law (whatever that law may be) which makes suicide a crime, must the neglect of health be a crime? For thus stand the two accounts:--By suicide you have cut off a _portion unknown_ from your life: years it may be, but possibly only days. By neglect of health you have cut off a _portion unknown_ from your life: days it may be, but also by possibility years. So the practical result may be the same in either case; or, possibly, the least is suicide. 'Yes,' you reply, 'the _practical_ results--but not the purpose--not the intention--_ergo_, not the crime.' Certainly not: in the one case the result arises from absolute predetermination, with the whole energies of the will; in the other it arises _in spite_ of your will, (meaning your choice)--it arises out of human infirmity. But still the difference is as between choosing a crime for its own sake, and falling into it from strong temptation.