Emily Dickinson Lexicon

A-RACH'NOID, a. [Gr. αραχνη, a spider, and ειδος, form; Heb. ארן, to weave, that is, to stretch, to draw out; Eng. reach.]

In anatomy, the arachnoid tunic, or arachnoid, is a semitransparent thin membrane which is spread over the brain and pia mater, and for the most part closely connected with the latter. The term has also been applied to that capsule of the crystaline lens, which is a continuation of the hyaloid membrane. – Cyc.