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.

150. Internal Meaning of Ezekiel, Chapter 27

1-2 Further concerning the church in respect to knowledges [cognitiones] of truth, which is Tyre. (2)

3-9 The Ancient Church had knowledges of truth and good of every kind and species, and by means of them it had intelligence. (2)

10-11 Truths that protected that church. (2)

12-13 Acquisitions and communications of all the knowledges. (2)

14-20 Knowledge [scientia], intelligence, and wisdom by means of them.

21-23 Divine worship from them. (2)

24-25 Truths and goods of every kind and thus everything of the church acquired by means of them. (2, 17)

26-29 Through natural knowledges [scientiae] they have perished. (2)

30-34 Lamentation over their destruction, (2)

35-36 and that it is the countenance of hell. (2)