Part 17

Light. A form of energy which is apprehended by the eye. It is supposed to move at a velocity of about 186,300 miles per second.

Limb. In astronomy, an edge or border. This is not the same word etymologically as the one which means an arm, a leg, or a wing.

Lithium. A metallic element. Symbol: Li.

Litmus. A substance which is turned red by acids and made blue again by bases. Paper stained with litmus is usually employed for such tests.

Logic. The science of thought. Scientific method.

Lutecium. A metallic element. Symbol: Lu.

Magnesium. A metallic element. Symbol: Mg.

Magnetize. To change into a magnet, give magnetic quality to, make capable of attracting iron.

Male. Of the sex or the organs that fecundate. Of a reproductive organ that fertilizes.

Mammal. One of the class of animals (Mammalia) which are vertebrate and which are distinguished by suckling their young.

Mandible. Jaw, especially the lower jaw. Part of a beak.

Manganese. A metallic element. Symbol: Mn.

Marsupial. One of an order of animals (Marsupialia) which are low mammals, and most of whose females carry the young in abdominal pouches.

Mass. Quantity of matter. This remains constant, but weight varies a little with geographical location.

Materia medica. The study of medicinal substances.

Mathematics. The science of space and quantity as such.

Matter. That which takes up space.

Mean. Equally removed from two extremes, average.

Mechanics. The science of motion. The study of the action of force on bodies. May be considered a branch of mathematics or of physics.

Medicine. The art of maintaining and restoring health. Surgery is sometimes excluded from the conception of medicine. The basis of medicine is only partially scientific.

Megacephalic. Large-headed.

Melt. To change from the solid to the liquid form.

Mendel’s Law. A principle formulated by Gregor Mendel with regard to the inheritance of characteristics. Fenton, following Walter, states it thus: “When two animals or plants unlike with respect to any character are crossed, the offspring of the first generation will be apparently like one of the parents in regard to the character in question. The parent which impresses its trait upon the offspring in this manner is called the dominant, while the one that fails to be visibly represented is the recessive. When, however, the hybrid progeny of this generation are in turn crossed with each other, they will produce a mixed lot of offspring, one-fourth of which will be like the dominant grandparent, one-fourth like the recessive one, and the remaining half like the parents which resembled the dominant grandparent, yet failed to breed true to it.”

Mercury. Of the metallic elements, the only one which is ordinarily found in the liquid state. Quicksilver. Formula: Hg.

Mesozoic. Relating to the geological period between the Paleozoic and the Cenozoic.

Metabolism. The complete process of building up and breaking down protoplasm in a living organism. The process of digesting and storing nutritive matter and of excreting waste matter.

Metal. An element which replaces or is capable of replacing the hydrogen of an acid. One of a class of substances typically ductile, malleable, lustrous, translucent only through very thin layers, conducting heat and electricity well.

Metaphysics. The branch of philosophy dealing with knowing and being. This must disappear entirely as science advances.