The lattice copies of $\ell_1$ in Banach lattices

summary:It is known that a Banach lattice with order continuous norm contains a copy of $\ell_1$ if and only if it contains a lattice copy of $\ell_1$. The purpose of this note is to present a more direct proof of this useful fact, which extends a similar theorem due to R.C. James for Banach spaces with unconditional bases, and complements the $c_0$- and $\ell_{\infty}$-cases considered by Lozanovskii, Mekler and Meyer-Nieberg