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POPULAR SCIENCE MONTHLY. 



themselves when only the ' good beasts ' are 

 selected to lie together." 



Play and DeTelopment. — In a paper on 

 play as a factor in development, published 

 in the American Physical Review for De- 

 cember, 1897, George A. Fitz, of Harvard 

 University, places himself upon the theory 

 now generally accepted by those who have 

 given the most careful study of the subject, 

 that play is simply the most important means 

 Nature has of preparing her children for 

 their life work. "We can readily see how 

 this has come about. The animals which 

 played were able to make a better fight for 

 existence, hence survived, and fixed in their 

 progeny the desire to play as an instinct. 

 Play is not merely the result of the acci- 

 dental desires of the individual ; it is a re- 

 sult of that natural selection which demands 

 everything serviceable to the preservation of 

 the species. Thus youth becomes more com- 

 pletely an apprenticeship to life, with play 

 as the master workman. All of Nature's 

 children play and are thereby prepared to 

 live ; not playing, they die. Granting, then, 

 that play is one of the most powerful in- 

 stincts in animal life, let us study its more 

 intimate relations to human life. How does 

 the child who plays vigorously and spontane- 

 ously diifer from the child who plays under 

 close restriction or not at all ? . . . He is 

 bom with an inherited tendency to grow into 

 the adult form, but this inherited force 

 toward development is not sufficiently strong 

 to produce unassisted more than a mimicry 

 of the best adult form, mental or physical. 

 The great law of development is the law of 

 use. No organ or tissue, no power of mus- 

 cle or brain, can be fully developed except 

 through use, through effort. In the play 

 of young animals we find all the conditions 

 of use necessary for their highest develop- 

 ment. In the spontaneous play of the child 

 with unrestricted opportunities, we find again 

 the conditions of use for all the tissues fully 

 satisfied." Further than this, the child is 

 habituated to make rapid judgments in the 

 presence of ever-changing relations ; there 

 is probably no factor so potent in the bal- 

 ance of the nervous system ; in its psychic 

 effects it gives a complete psycho-physiologi- 

 cal picture of pleasure. " In play, the child 

 is the unit of force; he initiates his own 



conditions. His limitations are self-imposed. 

 His self-control lies in execution rather than 

 inhibition. He is concerned with self ex- 

 pression rather than with self-repression. 

 Play thus relates itself to the truest con- 

 ception of education, the development of 

 power, the power of the individual to act as 

 a self-directed unit in civilization. The self- 

 control gained by play acts immediately, 

 strongly, and honestly in response to con- 

 ditions as they are presented in life." 



The Place of Plant Physiology.— Plant 



physiology, as briefly defined by Prof. D. T. 

 MacDougal, is concerned with the funda- 

 mental properties of the protoplasm of plants, 

 and the functions of the organisms into which 

 it is formed. It therefore includes the con- 

 sideration of all reactions of growth, move- 

 ment, metabolism, changes in form, insta- 

 bility, and other phenomena resulting from 

 the activity of forces internal to the plant. 

 It merges into morphology on one side, and 

 partly underlies oology on the other, and with 

 bacteriology and mycology forms the basis of 

 the study of pathology. Physiology and 

 chemistry join in the consideration of the 

 chemical activities and products of the or- 

 ganism, and the principles of physics are 

 involved in the investigation of the plant 

 machine. It is too otten slighted in schools 

 by being made a text-book and routine study. 

 "A systematic survey reveals the fact that, 

 instead of a complete and thorough plotting 

 of the great field of physiology, we have made 

 here and there a few simple trails through 

 the dense jungle of ungrouped and vaguely 

 defined principles, and the greater part of 

 the work is yet to be accomplished. The 

 fundamental problem of the constitution of 

 living matter still confronts us." We have 

 not yet succeeded in interpreting clearly even 

 tlie cruder visible phenomena of the cell. 

 The interprotoplastic threads have so far 

 received no conclusive interpretation. Nu- 

 merous problems relating to nutrition wait 

 for solution — the relations of chlorophyll, of 

 the nitro-bacteria, the acquisition of nitrogen, 

 the balance and combined action of the min- 

 eral elements in the soil, the formation and 

 work of the alkaloids, glucosides, pigment-!, 

 and other compounds in the plant, and the 

 ascent of sap, are only a part of the sub- 

 jects concerning which we are still in the 



