640 THE POPULAR SCIENCE MONTHLY. 



into certain chemical compounds, we can not infer from this that pro- 

 toplasm is one of these compounds. What characterizes a chemical 

 compound is fixity of composition. But protoplasm changes inces- 

 santly, without modifying any of its fundamental properties. New 

 substances are constantly entering into its mass while others are leav- 

 ing it. Protoplasm is perpetually decomposing and recomposing itself. 

 It is this, and not its chemical composition, that characterizes it. It 

 is always in movement, and motion characterizes life. 



Life is, then, only a combination of movements, or, if you please, a 

 mode of movement of which certain substances are alone capable, and 

 which is not without analogy with the whirling movements to which 

 eminent physicists attribute the properties of chemical atoms. We 

 might pursue this comparison between atoms and protoplasms, and use 

 it to show that the latter must have been formed originally in the 

 greatest possible number ; that we seem to be powerless to reproduce 

 them ; that they appeared with a train of properties which have con- 

 trolled their subsequent destiny ; and that they had from the first the 

 individuality we see in them at the present day. 



THE DUTY OF ENJOYMENT. 



TO say that we are under a moral obligation to enjoy ourselves 

 would be, in the opinion of most persons, to utter an unmeaning 

 paradox. It is commonly supposed that the natural instinct for plea- 

 sure can take care of itself without any reenforcement from a sense of 

 duty. More than this, our habits of thought instinctively lead us to 

 set duty in antagonism to pleasure, so that to talk of a duty of enjoy- 

 ment sounds self-contradictory. Many influences have combined in 

 the past history of our race to produce this conception of the relation 

 of pleasure and duty. Unless this idea had been developed and fixed 

 in the human mind, it is difiicult to see how the moral progress already 

 attained would have been possible. Even that extreme form of this 

 doctrine of the antagonism of pleasure and duty involved in the ascetic 

 renunciation of all enjoyment as sinful was doubtless a useful and 

 necessary belief in certain stages of social evolution. But it may be 

 that this conception of pleasure has now lost its utility, and will have 

 to be displaced by a view of life which sets a positive moral value on 

 enjoyment. The epicurean theory that all good resolves itself into 

 pleasure has long been before the world, and has won many adherents. 

 Since the revival of letters many writers have contended warmly 

 against the mediseval disparagement of pleasure. Of late years a 

 number of writers with a keen appreciation of the aesthetic resources 

 at our command have in beautiful and alluring language held up a 



