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POPULAR SCIENCE MONTHLY. 



ditions to human well-being and en- 

 joyment the value of which it would 

 be difficult to estimate, while the tele- 

 phone 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, iso- 

 lating those we wish to isolate and 

 leading others to form new and de- 

 sirable combinations. It has pro- 

 duced what is virtually a new article 

 of commerce in the metal alumini- 

 um, 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 con- 

 siderable treatise to set forth. The 

 bookmaker, the traveler, the astron- 

 omer, 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 succes- 

 sive 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 sci- 

 ence the physician's art has gained 

 a wonderful enlargement of its re- 

 sources. The mighty hunter of to- 

 day is not he who bags big game in 

 the African forest or the Indian jun- 

 gle, 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 dis- 

 posed to exclaim parodying a cele- 



brated saying "Cherchez le mi- 

 crobe!" Already a very consider- 

 able 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 con- 

 quests 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 gen- 

 eration. 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 Brit- 

 ish Association, tt that this feature of 

 internal secretion is confined to the 

 bodies mentioned ; it needs no spirit 

 of prophecy to foretell that the com- 

 ing 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 in- 

 timate 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 impor- 

 tance in the work of education, and 

 intelligent teachers are daily mak- 

 ing use of them to a greater or less 

 extent in the practice of their pro- 

 fession. There is a vast amount of 

 knowledge in the world to-day in 

 regard to the laws governing the 

 development of ideas and the acqui- 

 sition of knowledge, and as to the 

 specific differences between the child 



