In the case of the subject who inherits gout, a similar attention to the special conditions of healthy living suited to his case may insure great or complete freedom from the malady of his parent. Strict attention to dietary, the avoidance of all stimulants, and the participation in active, well-regulated exercise, form conditions which in a marked degree, if pursued conscientiously during youth, will ward off the tendency to develop the disease in question. In the case of an inherited tendency to mental disorders, mysterious and subtle as such tendency appears to be, it has been shown that strict attention to the education and upbringing of the child, a judicious system of education, the curbing of the passions, and the control of emotions, added to ordinary care in the selection of food and the physical necessities of life, may again insure the prolongation of life, and its freedom from one of the most terrible afflictions which can beset the human race. These considerations in reality constitute veritable triumphs of health-science; they show us that in his war against disease and death, man finds literally a saving knowledge in observance of the laws which science has deduced for the wise regulation of his life. It is ignorance or neglect of this great teaching which sends thousands of our fellow-mortals to an early grave, and which destroys hopes, ambitions, and opportunities that may contain in themselves the promise of high excellence in every department of human effort. The one great truth which health-reformers are never weary of proclaiming, because they know it is so true, consists in the declaration that the vast majority of the diseases which affect and afflict humanity are really of _preventable_ nature. Until this truth has been thoroughly driven home, and accepted alike by individuals and nations, no real progress in sanitary science can be expected or attained. To realise fully the immense power which the practical application of this thought places in our hands, we may briefly consider the causes of certain diseases, which in themselves though powerful and widespread, are nevertheless of _preventable_ kind. Amongst these diseases, those, popularly known as infectious fevers, and scientifically as zymotic diseases, stand out most prominently. We shall hereafter discuss the nature and origin, as far as these have been traced, of those ailments. Suffice it for the present to say, that science has demonstrated in a very clear fashion the possibilities of our escape from those physical terrors by attention to the conditions to which they owe their spread.