It is thus, that in Greece every thing tended to exalt the dignity of man, while in India every thing tended to depress it.276 To sum up the whole, it may be said that the Greeks had more respect for human powers; the Hindus for superhuman. The first dealt more with the known and available; the other with the unknown and mysterious.277 And by a parity of reasoning, the imagination, which the Hindus, being oppressed by the pomp and majesty of nature, never sought to control, lost its supremacy in the little peninsula of ancient Greece. In Greece, for the first time in the history of the world, the imagination was, in some degree, tempered and confined by the understanding. Not that its strength was impaired, or its vitality diminished. It was broken-in and tamed; its exuberance was checked, its follies were chastised. But that its energy remained, we have ample proof in those productions of the Greek mind which have survived to our own time. The gain, therefore, was complete; since the inquiring and sceptical faculties of the human understanding were cultivated, without destroying the reverential and poetic instincts of the imagination. Whether or not the balance was accurately adjusted, is another question; but it is certain that the adjustment was more nearly arrived at in Greece than in any previous civilization.278 There can, I think, be little doubt that, notwithstanding what was effected, too much authority was left to the imaginative faculties, and that the purely reasoning ones did not receive, and never have received, sufficient attention. Still, this does not affect the great fact, that the Greek literature is the first in which this deficiency was somewhat remedied, and in which there was a deliberate and systematic attempt to test all opinions by their consonance with human reason, and thus vindicate the right of Man to judge for himself on matters which are of supreme and incalculable importance.
I have selected India and Greece as the two terms of the preceding comparison, because our information respecting those countries is most extensive, and has been most carefully arranged. But every thing we know of the other tropical civilizations confirms the views I have advocated respecting the effects produced by the Aspects of Nature. In Central America extensive excavations have been made; and what has been brought to light proves that the national religion was, like that of India, a system of complete and unmitigated terror.279 Neither there nor in Mexico, nor in Peru, nor in Egypt, did the people desire to represent their deities in human forms, or ascribe to them human attributes. Even their temples are huge buildings, often constructed with great skill, but showing an evident wish to impress the mind with fear, and offering a striking contrast to the lighter and smaller structures which the Greeks employed for religious purposes. Thus, even in the style of architecture do we see the same principle at work; the dangers of the tropical civilization being more suggestive of the infinite, while the safety of the European civilization was more suggestive of the finite. To follow out the consequences of this great antagonism, it would be necessary to indicate how the infinite, the imaginative, the synthetic, and the deductive, are all connected; and are opposed, on the other hand, by the finite, the sceptical, the analytic, and the inductive. A complete illustration of this would carry me beyond the plan of this Introduction and would perhaps exceed the resources of my own knowledge; and I must now leave to the candour of the reader what I am conscious is but an imperfect sketch, but what may, nevertheless, suggest to him materials for future thought, and, if I might indulge the hope, may open to historians a new field, by reminding them that every where the hand of Nature is upon us, and that the history of the human mind can only be understood by connecting with it the history and the aspects of the material universe.
As these views have a social and economical importance quite independent of their physiological value, I will endeavour, in this note, to fortify them still further, by showing that the connexion between carbonized food and the respiratory functions may be illustrated by a wider survey of the animal kingdom.
The gland most universal among the different classes of animals is the liver;280 and its principal business is to relieve the system of its superfluous carbon, which it accomplishes by secreting bile, a highly carbonized fluid.281 Now, the connexion between this process and the respiratory functions is highly curious. For, if we take a general view of animal life, we shall find that the liver and lungs are nearly always compensatory; that is to say, when one organ is small and inert, the other is large and active. Thus, reptiles have feeble lungs, but a considerable liver;282 and thus, too, in fishes, which have no lungs, in the ordinary sense of the word, the size of the liver is often enormous.283 On the other hand, insects have a very large and complicated system of air tubes; but their liver is minute, and its functions are habitually sluggish.284 If, instead of comparing the different classes of animals, we compare the different stages through which the same animal passes, we shall find further confirmation of this wide and striking principle. For the law holds good even before birth; since in the unborn infant the lungs have scarcely any activity, but there is an immense liver, which is full of energy and pours out bile in profusion.285 And so invariable is this relation, that in man the liver is the first organ which is formed: it is preponderant during the whole period of fœtal life; but it rapidly diminishes when, after birth, the lungs come into play, and a new scheme of compensation is established in the system.286
These facts, interesting to the philosophic physiologist, are of great moment in reference to the doctrines advocated in this chapter. Inasmuch as the liver and lungs are compensatory in the history of their organization, it is highly probable that they are also compensatory in the functions they perform; and that what is left undone by one will have to be accomplished by the other. The liver, therefore, fulfilling the duty, as chemistry teaches us, of decarbonizing the system by secreting a carbonized fluid, we should expect, even in the absence of any further evidence, that the lungs would be likewise decarbonizing; in other words, we should expect that if, from any cause, we are surcharged with carbon, our lungs must assist in remedying the evil. This brings us, by another road, to the conclusion that highly carbonized food has a tendency to tax the lungs; so that the connexion between a carbonized diet and the respiratory functions, instead of being, as some assert, a crude hypothesis, is an eminently scientific theory, and is corroborated not only by chemistry, but by the general scheme of the animal kingdom, and even by the observation of embryological phenomena. The views of Liebig, and of his followers, are indeed supported by so many analogies, and harmonize so well with other parts of our knowledge, that nothing but a perverse hatred of generalization, or an incapacity for dealing with large speculative truths, can explain the hostility directed against conclusions which have been gradually forcing themselves upon us since Lavoisier, seventy years ago, attempted to explain the respiratory functions by subjecting them to the laws of chemical combination.
In this, and previous notes (see in particular notes 30, 31, 35), I have considered the connexion between food respiration, and animal heat, at a length which will appear tedious to readers uninterested in physiological pursuits; but the investigation has become necessary, on account of the difficulties raised by experimenters, who, not having studied the subject comprehensively, object to certain parts of it. To mention what, from the ability and reputation of the author, is a conspicuous instance of this, Sir Benjamin Brodie has recently published a volume (Physiological Researches, 1851) containing some ingeniously contrived experiments on