Du´ra Ma´ter (L.). Literally, the hard mother; the tough membrane which envelops the brain.

Dys-pep´si-a (Gr. δυς, dus, difficult, and πέπτω, pep´to, to digest). Difficult or painful digestion; a disordered condition of the stomach.

E-mul´sion (L. emul´geo, to milk). Oil in a finely divided state suspended in water.

En-am´el (Fr. email). The dense material which covers the crown of the tooth.

En´er-gy, Specific, of a Nerve. When a nerve of special sense is excited, whatever be the cause, the sensation experienced is that peculiar to the nerve; this is said to be the law of the specific energy of the nerves.

Ep-i-glot´tis (Gr. ἐπί, epi, upon, and γλωττις, glottis, the entrance to the windpipe). A leaf-shaped piece of cartilage which covers the top of the larynx during the act of swallowing.

Ex-cre´tion (L. excer´no, to separate). The separation from the blood of the waste particles of the body; also the materials excreted.

Ex-pi-ra´tion (L. expi´ro, to breathe out). The act of forcing air out of the lungs.

Ex-ten´sion (L. ex, out, and ten´do, to stretch). The act of restoring a limb, etc., to its natural position after it has been flexed, or bent; the opposite of Flexion.