Among the domestic animals known to the Rigveda those of lesser importance are sheep, goats, asses, and dogs. The latter, it may be gathered, were used for hunting, guarding, and tracking cattle, as well as for keeping watch at night. Cattle, however, occupy the chief place. Cows were the chief form of wealth, and the name of the sacrificial "fee," [8] dakshina, is properly an adjective meaning "right," "valuable," with the ellipse of go, "cow." No sight gladdened the eye of the Vedic Indian more than the cow returning from the pasture and licking her calf fastened by a cord; no sound was more musical to his ear than the lowing of milch kine. To him therefore there was nothing grotesque in the poet exclaiming, "As cows low to their calves near the stalls, so we will praise Indra with our hymns," or "Like unmilked kine we have called aloud (lowed) to thee, O hero (Indra)." For greater security cows were, after returning from pasture, kept in stalls during the night and let out again in the morning. Though the cow-killer is in the White Yajurveda already said to be punishable with death, the Rigveda does not express an absolute prohibition, for the wedding-hymn shows that even the cow was slaughtered on specially solemn occasions, while bulls are several times described as sacrificed to Indra in large numbers. Whilst the cows were out at pasture, bulls and oxen were regularly used for the purpose of ploughing and drawing carts. Horses came next in value to cattle, for wealth in steeds is constantly prayed for along with abundance of cows. To a people so frequently engaged in battle, the horse was of essential value in drawing the war-car; he was also indispensable in the chariot-race, to which the Vedic Indian was devoted. He was, however, not yet used for riding. The horse-sacrifice, moreover, was regarded as the most important and efficacious of animal sacrifices. Of the birds of the Rigveda I need only mention those which have some historical or literary interest. The wild goose or swan (hamsa), so familiar to the classical poets, is frequently referred to, being said to swim in the water and to fly in a line. The curious power of separating soma from water is attributed to it in the White Yajurveda, as that of extracting milk from water is in the later poetry. The latter faculty belongs to the curlew (krunch), according to the same Veda. The chakravaka or ruddy goose, on the fidelity of which the post-Vedic poets so often dwell, is mentioned once in the Rigveda, the Açvins being said to come in the morning like a couple of these birds, while the Atharva-veda already refers to them as models of conjugal love. Peahens (mayuri) are spoken of in the Rigveda as removing poison, and parrots (çuka) are alluded to as yellow. By the time of the Yajurveda the latter bird had been tamed, for it is there described as "uttering human speech."