a soul like an anchovy?

[KuaiLe]

Read this conversation from Mirror, Mirror by Gregory Maguire:
"I'd no more leave her in your care than I would my own soul."
"Hmmmmph, I've never been persuaded you had much of a soul. More like a little damp anchovy stuck between your breasts, trying to breathe. That's what you smell like, anyway."
Why did he suddenly talk about a damp anchovy and how the other person smells like? The conversation seems to jump from one topic to another and I am completely lost...

[Casiopea]

Speaker A insults speaker B, so speaker B insults A:

A: "I'd no more leave her in your care than I would my own soul."
<A thinks B is an incompetent care-giver; A wouldn't trust B to care for anyone or anything, including A's soul>

B: "Hmmmmph, I've never been persuaded you had much of a soul."
<B insults A by implying that A lacks character/heart; i.e., 'you [don't have] much of a soul'.>

B: "More like a little damp anchovy stuck between your breasts, trying to breathe. That's what you smell like, anyway."
< B describes A's heart/soul as a saltwater dwelling small plankton-feeding fish that smells rather bad.>

[KuaiLe]

Thanks a lot! It's very clear!