Another medium of expression that students may profitably employ is drawing. This is especially valuable in such subjects as geology, physiology and botany. Students in botany are compelled to do much drawing of the plant-forms which they study, and this is a wise requirement, for it makes them observe more carefully, report more faithfully and recall with greater ease. You may secure the same advantages by employing the graphic method in other studies. For example, when reading in a geology text-book about the stratification of the earth in a certain region, draw the parts described and label them according to the description. You will be surprised to see how clear the description becomes and how easily it is later recalled. Let us examine the effects of the expressive movements of speech, writing and the like, and see the mechanism by which they facilitate the study process. We may describe their effects in two ways: neurologically and psychologically. As may be expected from our preliminary study of the nervous system, we see their first effects upon the motor pathways leading out to the muscles. Each passage of the nerve current from brain to muscle leaves traces so that the resulting act is performed with greater ease upon each repetition. This fact has already been emphasized by the warning, Guard the avenues of expression. Especially is it important at the first performance of an act, because this determines the path of later performances. In such studies as piano-playing, vocalizing and pronunciation of foreign words, see that your first performance is absolutely right, then as the expressive movements are repeated, they will be more firmly ingrained because of the deepening of the motor pathways.