And, as a corollary to this, it may be stated that this increase--this enhancement of therapeutic effect--is, within physiological limits, in the ratio of the atmospheric condensation. By physiological limits we mean simply that there is a degree of atmospheric condensation beyond which we cannot go without jeopardizing the well-being of the subject. (_To be continued_.) * * * * * EYESIGHT: ITS CARE DURING INFANCY AND YOUTH.[1] [Footnote 1: A lecture delivered before the Franklin Institute, December 5, 1890.--_From the Journal of the Institute_.] By L. WEBSTER FOX, M.D. Medical science, as taught in our medical colleges to-day, has two objects in view: (1) the prevention of disease; (2) the amelioration of disease and its cure. Some of our advanced thinkers are suggesting a new mode of practice, that is the prevention of disease by proper hygienic measures. Chairs are being established and professors appointed to deliver lectures on hygiene. Of what value is the application of therapeutics if the human economy is so lowered in its vital forces that dissolution is inevitable? Is it not better to prevent disease than to try the cure after it has become established, or has honeycombed the constitution? These few preliminary remarks are _apropos_ to what is to follow in the subject which I have selected as the topic for discussion this evening. Vision is the most useful of all the senses. It is the one gift which we should cherish and guard the most. And at no time in one's life is it more precious than in infancy and youth.