Yes, not every part of the snail can be eaten. You can eat the hard part near the mouth of the snail, but you can't eat the soft part at the bottom of the snail, because it is easy for these parts to integrate some harmful substances and parasites.

Eating snails need to pay attention to:

Pick live snails. With a finger pressure cover, can pop up is live, no elasticity is dead, the weather is hot dead rot too fast can never eat.

If you are making your own snails, buy back the snails with scissors and remove the tail, put a drop of sesame oil in the water and leave it for 20 minutes or so so to make the snails spit out the mud and sand and lure out the parasites. In the past a little water to make it more clean.