The Fabric of a Heart

What's the fabric of a heart? Mine's certainly not steel
With the velvet, suede, tissue emotions I feel.
And is it even solid, what's its current state?
When melting or of ice, the temp reads 38.
I once had a meeting, trying to sell something
He told me "your lot don't have a heart, just a brick on a string."
You say that yours is broken, well I don't know what you mean
It pumps or it doesn't, there's nothing inbetween.
Maybe I'm just a cynic, something of that art
Heart of stone, maybe, brings me back to the start