GUYER] THE Q URS TION OF ME TIfOD IN NA TURES TUD V 231 



present before the food can be used by the tisst^es. With very- 

 young pupils it would not be desirable, of course, to attempt to 

 lead out the more intricate topics of digestion or of other physio- 

 logical functions. It should be noted, however, that the whole 

 question of digestion, circulation, etc., can be brought out in a 

 very interesting manner for students of physiology by such an 

 interpretative method. The emphatically important thing, 

 whether in nature-study or physiology, is that the interpretation 

 be made by the child, not by the teacher. The latter should 

 simply guide by means of relevant questions. 



It is needless to take the space for a detailed discussion of self- 

 protection and the remaining subjects of the synopsis, because 

 the many simple interpretations along these lines which children 

 may be led to make, are obvious. It may not be amiss, however, 

 to indicate briefly a few of the more general topics. 



In defending themselves, some animals, of course, frequently 

 make use of the same weapons as serve them in securing their 

 food. Such structures, on the other hand, as the armor of the 

 turtle or of the armadillo, or the barbed spines of the porcupine, 

 are instances of organs more exclusively protective in nature. 

 Besides the many obvious examples of armor, of fleetness or of 

 strength which serve to protect various animals, much of the color 

 observable would come under the heading of protection from 

 enemies. 



Many of the most evident adaptations of animals are concerned 

 perhaps, with adjustment to physical surroundings such as, for 

 example, the element in which the animal dwells. Thus, animals 

 such as fishes, which live in water, must have mechanisms for 

 breathing or for locomotion necessarily very different from those 

 which are terrestrial in habit. Again, flying forms require a type 

 of propelling organs different from that of forms which walk 

 upon the surface of the earth. It is this necessity for physical 

 adjustment, furthermore, that gives rise in cold climates, to the 

 furs, fleeces and downs to be met with in such profusion. Not 

 only structure, indeed, but habits as well, vary under different 

 climatic conditions. The hibernation practiced by some animals 

 is a good example of adjustment to climate by means of habit. 

 It will be found that many structures which may be looked upon 

 as coming under the heading of adjustment to physical surround- 

 ings, may also be considered from another aspect under the topic 

 of food. 



