। ॥ १९ ॥
In plain words
The body is a heap: blood, the three humours, marrow, fat, flesh, bone. It is tied shut on the outside with skin — and that is the only reason the crows are not eating it.
Close to the Sanskrit
The body is an aggregate of blood, the three humours, marrow, fat, flesh, and bone. It, bound up on the outside by skin, is therefore not eaten by crows.