οὐκ ἂν λάβοις παρὰ τοῦ μὴ ἔχοντος → you can't take from one who doesn't have, you can't squeeze blood out of a turnip, you can't get blood out of a turnip, you can't get blood from a stone, you can't get blood out of a stone
grăvĭtūdo: ĭnis, f. gravis,
I a cold in the head, catarrh (very rare): sine ructu et gravitudine, Apic. 3, 6, 76: arterica, Vitr. 1, 6, 3.