Page:Popular Science Monthly Volume 52.djvu/278

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ditions to human well-being and enjoyment the value of which it would be difficult to estimate, while the telephone has almost revolutionized the industrial and commercial life of cities and towns. Electro-chemistry, again, and photography are two arts the influence of which is at once widespread and penetrating. The former dissociates the elements, isolating those we wish to isolate and leading others to form new and desirable combinations. It has produced what is virtually a new article of commerce in the metal aluminium, previously a rare and expensive product, and in a thousand ways has transformed or modified industrial processes. What photography is to the present age it would take a considerable treatise to set forth. The bookmaker, the traveler, the astronomer, the physician, the analyist, the architect, the biologist, the police agent, the engineer, the microscopist, the military man, the artist, and the representatives of a hundred other crafts and professions would all have to contribute to the tale. By photography we can record successive moments in the impact of a cannon ball and analyze the life history of a lightning flash; we pierce the abysmal depths of space and catch the faintly trembling rays of bodies that no telescope has the power to reveal.

With the general advance of science the physician's art has gained a wonderful enlargement of its resources. The mighty hunter of to-day is not he who bags big game in the African forest or the Indian jungle, but he Who, following in the steps of Pasteur and Koch, tracks the pathogenic microbe to its lair and studies to render it innocuous. When anything nowadays goes wrong with the physical organism, the man of scientific mind is disposed to exclaim—parodying a celebrated saying—"Cherchez le microbe!" Already a very considerable knowledge and mastery have been gained of these extraordinary agents, so utterly unknown to the science of the past; and there is no reason to doubt that great conquests are yet to be won in this particular line of research. But other lines of investigation only less important in their bearing on the preservation of life and health have been opened up within the past generation. Of these scarcely any is more interesting than that which has led to the discovery of the "internal secretion" carried on by such organs as the pancreas, the thyroid gland, and the suprarenal capsules. "No one can suppose," said Professor Foster, in his recent address before the British Association, "that this feature of internal secretion is confined to the bodies mentioned; it needs no spirit of prophecy to foretell that the coming years will add to physiological science a large and long chapter, the first verses of which belong to the dozen years that have passed away."

If we pass over to the region of psychology, we find that there, too, a notable advance has been made both in methods and in results. Mind is being treated scientifically as something correlated in the most intimate manner with the body, and for all practical purposes a function of a certain kind of organized matter. The observations which have been made from this point of view are undoubtedly of the highest importance in the work of education, and intelligent teachers are daily making use of them to a greater or less extent in the practice of their profession. There is a vast amount of knowledge in the world to-day in regard to the laws governing the development of ideas and the acquisition of knowledge, and as to the specific differences between the child