2 INTRO D UCTOR Y. 



and has there assumed, for a time, the living state. Lifeless mat- 

 ter in the shape of food is continually streaming into all living 

 things on the one hand and passing out again as waste on the 

 other. In its journey through the organism some of this mat- 

 ter enters into the living state and lingers for a time as part of 

 the bodily substance. But sooner or later it dies, and is then for 

 the most part cast out of the body (though a part may be retained 

 within it, either as an accumulation of waste material, or to serve 

 some useful purpose). Matter may thus pass from the lifeless 

 into the living state and back again to the lifeless, over and over 

 in never-ending cycles. A living plant or animal is like a whirl- 

 pool into which, and out of which, matter is constantly stream- 

 ing, while the whirlpool maintains its characteristic form and 

 individuality.* 



How then is living matter different from lifeless matter? The 

 question cannot be fully answered by chemical analysis, for the 

 reason that this process necessarily kills living matter, and the 



* We append Huxley's graphic comparison of a living organism to a whirl- 

 pool (The Crayfish as an Introduction to the Study of Zoology, pp. 84, 85. Ap- 

 pleton, N. Y., 1880), having made slight verbal cnanges so that the passage, 

 originally applied to a particular animal, the crayfish, may be made general: 



" To put the matter in the most general shape, the body of the organism 

 is a sort of focus to which certain material particles converge, in which they 

 move for a time, and from which they are afterward expelled in new combina- 

 tions. The parallel between a whirlpool in a stream and a living being, which 

 has often been drawn, is as just as it is striking. The whirlpool is permanent, 

 but the particles of water which constitute it are incessantly changing. Those 

 which enter it on the one side are whirled around and temporarily constitute 

 a part of its individuality; and as they leave it on the other side, their places 

 are made good by newcomers 



" Those who have seen the wonderful whirlpool, three miles below the Falls 

 of Niagara, will not have forgotten the heaped-up wave which tumbles and 

 tosses, a very embodiment of restless energy, where the swift stream hurrying 

 from the Falls is compelled to make a sudden turn toward Lake Ontario. 

 However changeful in the contour of its crest, this wave has been visible, 

 approximately in the same place and with the same general form, for centuries 

 past. Seen from a mile off it would appear to be a stationary hillock of 

 water. Viewed closely it is a typical expression of the conllicting impulses 

 generated by a swift rush of material particles. 



" Now, with all our appliances, we cannot get within a good many miles, so 

 to speak, of the living organism. If we could, we should see that it was noth- 

 ing but the constant form of a similar turmoil of material molecules, which 

 arc constantly flowing into the organism on the one side and streaming out 

 on the other." 



