"When in active use," says Mitchell, "the thinking organs become full of blood, and, as Dr. Lombard has shown, rise in temperature, while the feet and hands become cold. Nature meant that for their work they should be, in the first place, supplied with food; next, that they should have certain intervals of rest to rid themselves of the excess of blood accumulated during their periods of activity; and this is to be done by sleep, and also by bringing into play the physical machinery of the body, such as the muscles--that is to say, by exercise which flushes the parts engaged in it, and so depletes the brain."[H] Here, then, some physical exercise will rest his brain, and fit it for more and better work. But this does not necessarily imply so much as is called for in the hour. Happily, however, there is no lack of instances where work, quite as vigorous, though not as well directed, has accompanied mental work of a very high order, and to all appearances has been a help rather than a hinderance. Instead of one hour a day, Napoleon for years was in the saddle several hours almost daily, but we never heard that it clogged his mind. Charles O'Conor, always fond of long walks, is good at them to-day, and noticeably erect and quick of movement, though for weeks he once lay at death's door, and though he was born in 1804. James Russell Lowell, sturdy, broad, and ruddy, is said to never ride when he can walk, and he is nearly sixty. Gladstone's reputation as an axeman among the Hawarden oaks has reached our shores. Indeed, it is doubtful if there are many better _fellers_ of his age in Europe, and he was born in 1809. Mr. M.H. Beebee, the present senior tutor at Cambridge University in England, who rowed at number two in the "'Varsity" eight against Oxford in '65, not only took the very highest university honor--a double-first--but a much higher double-first than even Gladstone had taken years before. The fencing, duelling, and hard riding of Bismarck's youth do not seem to have perceptibly dimmed his intellect, or to have unfitted it for enormous and very important work in later life. And while the in-door work equalizes the strength, and takes care of the arms and chest, the hour's "constitutional" daily out-of-doors has an especial advantage, in that it insures at least that much out-of-door life and air. Dr. Mitchell says, "When exposure to out-of-door air is associated with a fair share of physical exertion, it is an immense safeguard against the ills of anxiety and too much brain-work. I presume that very few of our generals could have gone through with their terrible task if it had not been that they lived in the open air and exercised freely. For these reasons I do not doubt that the effects of our great contest were far more severely felt by the Secretary of War and the late President than by Grant or Sherman."