Still stronger, however, becomes the argument, when we find that the same individual animal is capable of more or less exertion according as its food is more or less nutritious.  This has been demonstrated in the case of the horse.  Though flesh may be gained by a grazing horse, strength is lost; as putting him to hard work proves.  “The consequence of turning horses out to grass is relaxation of the muscular system.”  “Grass is a very good preparation for a bullock for Smithfield market, but a very bad one for a hunter.”  It was well known of old that, after passing the summer in the fields, hunters required some months of stable-feeding before becoming able to follow the hounds; and that they did not get into good condition till the beginning of the next spring.  And the modern practice is that insisted on by Mr. Apperley—­“Never to give a hunter what is called ‘a summer’s run at grass,’ and, except under particular and very favourable circumstances, never to turn him out at all.”  That is to say, never give him poor food:  great energy and endurance are to be obtained only by the continued use of nutritive food.  So true is this that, as proved by Mr. Apperley, prolonged high-feeding enables a middling horse to equal, in his performances, a first-rate horse fed in the ordinary way.  To which various evidences add the familiar fact that, when a horse is required to do double duty, it is the practice to give him beans—­a food containing a larger proportion of nitrogenous, or flesh-making material, than his habitual oats.

Once more, in the case of individual men the truth has been illustrated with equal, or still greater, clearness.  We do not refer to men in training for feats of strength, whose regimen, however, thoroughly conforms to the doctrine.  We refer to the experience of railway-contractors and their labourers.  It has been for years a well-established fact that an English navvy, eating largely of flesh, is far more efficient than a Continental navvy living on farinaceous food:  so much more efficient, that English contractors for Continental railways found it pay to take their labourers with them.  That difference of diet and not difference of race caused this superiority, has been of late distinctly shown.  For it has turned out, that when the Continental navvies live in the same style as their English competitors, they presently rise, more or less nearly, to a par with them in efficiency.  And to this fact let us here add the converse one, to which we can give personal testimony based upon six months’ experience of vegetarianism, that abstinence from meat entails diminished energy of both body and mind.