Rhythm, or the graduated and alternate action and reaction with which a vibration begins and ends, is a universal law in the manifestation and movements of all natural phenomena; a law which is revealed on a grand scale in all the recurring periods of nature, whether astral, telluric, or meteorological, as well as in the form and manifold phases of organisms and their modes of reproduction.  This universal law also applies to the whole mental and organic system of animals and men, whenever they become conscious of their own existence.  The same universal rhythm constitutes the fundamental form of sound in the vibration of metallic bars, or of strings, and becomes perceptible to the external senses by means of our organ of hearing, as also by the external and innate necessity slowly developed by our habits of consciousness, which may be termed the external causes of its organic evolution and constitution.

By these organic and cosmic tendencies, and by the intrinsic impulse towards modulation of sound already explained, speech first issued from the human breast in harmonious accents and rhythmic form, and these became in their turn the causes and genesis of versification and metre.  The classic experiments of Helmholtz show that each note may be regarded as a harmonic whole, owing to the complementary sounds which accompany it in its complete development.  With reference to our own race, the genesis of the composition of verse and metre are shown by the researches made by Westphal and others into the metrical system of the Vedic Aryans, the Turanians, and the Greeks, since the fact that their metres were the same implies a common origin.  The demonstration is complete, if we compare the iambic metre of Archilochus with that of the Vedic hymns.  There are in both three series of iambuses—­the dimeter, the cataleptic trimeter, and the acataleptic.[36]

This observation applies to the physical and physiological conditions of the phenomenon, since primitive men could not speak without rhythmic modulation of words.  We are not quite without hope of discovering by induction the origin of wind or stringed instruments which accompanied the songs, after the specification of the modes of speech was so far advanced as to distinguish singing—­which had already become an art—­from the daily necessity of reciprocal communication in words.  In this research we must proceed step by step, aided by minute observation, lest we should accept an hypothesis which does not correspond with the facts.

Not only man, but some animals—­among others a species of mouse found in South Africa—­naturally uses his limbs to moderate or strengthen the light of vision.  This mouse was observed to shade its eyes with its forepaws in order to look at some distant object under a blazing sun, as we should do in like conditions.  In man, whose arms and hands are readily adapted to this primitive art, the habit is common, even among the rudest savages.  Putting