Mucus. The glairy fluid secreted by mucous membranes.
Myopia (Gr. μύω, to shut, and ὤψ, the eye). A defect of vision dependent upon an eyeball that is too long, rendering distant objects indistinct; near sight.
Myosin (Gr. μῶς, muscle). Chief proteid substance of muscle.
Narcotic (Gr. ναρκάω, to benumb). A medicine which, in poisonous doses, produces stupor, convulsions, and sometimes death.
Nerve Cell. A minute round and ashen-gray cell found in the brain and other nervous centers.
Nerve Fiber. An exceedingly slender thread of nervous tissue.
Nicotine. The poisonous and stupefying oil extracted from tobacco.
Nostril (Anglo-Saxon nosu, nose, and thyrl, a hole). One of the two outer openings of the nose.
Nucleolus (dim. of nucleus). A little nucleus.
Nucleus (Lat. nux, a nut). A central part of any body, or that about which matter is collected. In anatomy, a cell within a cell.