The heart means love. A good heart means love to the Lord and to the neighbor, while a hard or stony heart means the love of self or the world -- riches and things. When the psalmist asks the Lord to search his heart, he wants the Lord to see what it is that he loves. And we are what we love. What we eat may form our earthly body, but it's only temporary, what we love forms our spiritual body, beautiful or ugly as we have chosen. It's interesting to note that the first multi-cellular motion of our embryo is the pulsating that starts in a twist of blood vessel that is to become our heart, and the last motion of our natural body is our heartbeat. It is there for all of our natural life. And of course there is a beating heart in our spiritual bodies when we come to put them on.

In Genesis 1:24, beasts signify the things of man's will or loves. (Arcana Coelestia 44, 46)

In Genesis 9:10, beasts signify all that was living in the man of the Ancient Church, and also what belonged to his new will; likewise the lower things of his understanding and the will therefrom. (Arcana Coelestia 1026-1029)

In Psalm 104:20, beasts signify affections longing to be instructed, or spiritually nourished. (Apocalypse Explained 650[10])

In Luke 10:35, since the beast was a donkey, this signifies to instruct another according to his capability. (Apocalypse Explained 1154)

The beast of the south (Isaiah 30:6) signifies people who are principled in the knowledges of good and of truth, but do not apply them to life and instead to science.

Every beast and creeping thing (Genesis 8:19) signifies the goodnesses of the internal and external man.

"Beasts" represent the affection for doing good things, a true desire to do them from the heart. In the negative sense, "beasts" stand for the lust to do evil.

The beast ascending out of the sea (Revelation 13:1) signifies reasonings from the natural man confirming the separation of faith from life.

(Referencat: Apocalypse Explained 13, 773; Revelation 13:11)