[47] “The deleterious effect of tobacco upon eyesight is an acknowledged fact. The Belgian government instituted an investigation into the cause of the prevalence of color-blindness. The unanimous verdict of the experts making the examination was that the use of tobacco was one of the principal causes of this defect of vision. “The dimness of sight caused by alcohol or tobacco has long been clinically recognized, although not until recently accurately understood. The main facts can now be stated with much assurance, since the publication of an article by Uhthoff which leaves little more to be said. He examined one thousand patients who were detained in hospital because of alcoholic excess, and out of these found a total of eye diseases of about thirty per cent. “Commonly both eyes are affected, and the progress of the disease is slow, both in culmination and in recovery.... Treatment demands entire abstinence.”—Henry D. Noyes, Professor of Otology in the Bellevue Hospital Medical College, New York. [48] “The student who will take a little trouble in noticing the ears of the persons whom he meets from day to day will be greatly interested and surprised to see how much the auricle varies. It may be a thick and clumsy ear or a beautifully delicate one; long and narrow or short and broad, may have a neatly formed and distinct lobule, or one that is heavy, ungainly, and united to the cheek so as hardly to form a separate part of the auricle, may hug the head closely or flare outward so as to form almost two wings to the head. In art, and especially in medallion portraits, in which the ear is a marked (because central) feature, the auricle is of great importance”—William W. Keen, M.D., editor of Gray’s _Anatomy_. [49] The organ of Corti is a very complicated structure which it is needless to describe in this connection. It consists essentially of modified ephithelial cells floated upon the auditory epithelium, or basilar membrane, of the cochlea. There is a series of fibers, each made of two parts sloped against each other like the rafters of a roof. It is estimated that there are no less than 3000 of these arches in the human ear, placed side by side in a continuous series along the whole length of the basilar membrane. Resting on these arches are numbers of conical epithelial cells, from the free surface of which bundles of stiff hairs (cilia) project. The fact that these hair-cells are connected with the fibers of the cochlear division of the auditory nerve suggests that they must play an important part in auditory sensation. [50] The voices of boys “break,” or “change,” because of the sudden growth or enlargement of the larynx, and consequent increase in length of the vocal cords, at from fourteen to sixteen years of age. No such enlargement takes place in the larynxes of girls: therefore their voices undergo no such sudden change.