Experiment 182._To illustrate imperfect visual judgments_. Make three round black dots, A, B, C, of the same size, in the same line, and let A and C be equidistant from B. Between A and B make several more dots of the same size. A and B will then appear to be farther apart than B and C. Illustration: For the same reason, of two squares absolutely identical in size, one marked with alternately clear and dark cross-bands, and the other with alternately clear and dark upright markings, the former will appear broader and the latter higher than the other. Experiment 183. Make on a white card two squares of equal size. Across the one draw _horizontal_ lines at equal distances, and in the other make similar _vertical_ lines. Hold them at some distance. The one with horizontal lines appears higher than it really is, while the one with vertical lines appears broader, _i.e._, both appear oblong. Experiment 184. Look at the row of letters (S) and figures (8). To some the upper halves of the letters and figures may appear to be of the same size as the lower halves, to others the lower halves may appear larger. Hold the figure upside down, and observe that there is a considerable difference between the two, the lower halves being considerably larger. S S S S S S S S 8 8 8 8 8 8 8 8 Experiment 185. _To illustrate imperfect visual judgment_. The length of a line appears to vary according to the angle and direction of certain other lines in relation to it (Fig. 147). The length of the two vertical lines is the same, yet B appears much longer than A. Illustration: Fig. 147.—To show False Estimate of Size. Experiment 186. In indirect vision the appreciation of direction is still more imperfect. While leaning on a large table, fix a point on the table, and then try to arrange three small pieces of colored paper in a straight line. Invariably, the papers, being at a distance from the fixation-point, and being seen by indirect vision, are arranged, not in a straight line, but in the arc of a circle with a long radius. Chapter XII. The Throat and the Voice. 349. The Throat. The throat is a double highway, as it were, through which the air we breathe traverses the larynx on its way to the lungs, and through which the food we swallow reaches the œsophagus on its passage to the stomach. It is, therefore, a very important region of the body, being concerned in the great acts of respiration and digestion. The throat is enclosed and protected by various muscles and bony structures, along which run the great blood-vessels that supply the head, and the great nerve trunks that pass from the brain to the parts below. We have already described the food passages (Chapter VI.) and the air passages (Chapter VIII.).