Who are common men? Women class, as a class; and Śūdra, laborer class, working class; and strī-śūdra-dvijabandhūnaṁ, and dvija means twice-born, the higher caste. The higher caste means they must be twice-born. How is that? One birth is father and mother, real father and mother, and the next birth is spiritual master and the Vedas. That means when one is trained up in the matter of real knowledge—Veda means real knowledge—by the guidance of the spiritual master, he is supposed to be twice-born.
So dvija-bandhu. Twice-born means cultural society. Those who have Vedic cultured, those who have followed the Vedic principles rigidly, it doesn't matter whether he is a householder or a brahmacārī or a sannyāsī. There are eight divisions of human society: four divisions social structure, and four divisions for spiritual enlightenment. So unless the eight divisions are properly managed, that is not human society. Human society is distinct from animal society by culture. What is that culture? Vedic culture, knowledge. Vedic means knowledge. One must be equipped with full knowledge.
"So this Vedic culture," Vyāsadeva says, "or the Vedic principles, are not very easily understood by women class, by worker class and dvija-bandhu." Dvija-bandhu means the boys who have taken birth in the family who are supposed to be very cultured, but their habit is different. They are called dvija-bandhu.
In every country, that deterioration of social structure has already begun. They are called varṇa-saṅkara. Varṇa-saṅkara actually means that those who are illiterate. So for them it is very difficult to understand the Vedic principles. Therefore the same knowledge is described in stories just like Mahābhārata, Purāṇas, and for understanding of all men, all women. So Mahābhārata is especially written for such class of men and women. And the hero of Mahābhārata is Arjuna. Similarly, the hero of Śrīmad-Bhāgavatam is Arjuna's grandson, Mahārāja Parīkṣit, King Parīkṣit.
Now the history of Śrīmad-Bhāgavatam is like this, that Parīkṣit Mahārāja was a great king, emperor of the world, very pious devotee, all qualified. So sometimes he went to the forest for hunting. The hunting is allowed to the Kṣatriyas, kings, royals, kings. Why? Because a king has to look after administration of the society; therefore sometimes he has to order to kill some man, "Hang this man." Or sometimes he will take the sword in his own hand and kill the culprit, criminal, immediately.
So therefore the killing practice was allowed to the Kṣatriyas, royal family. Therefore sometimes the king would go into the forest and kill some animals to practice. Just like in the medical laboratory, physiological laboratory, some animals are tested to see the physiological condition of the body, similarly, always these experiments are made on the animals.