290 



SCIENCE 



[N. S. Vol. XXXVI. No. 923 



hitherto been regarded, so that the diffi- 

 culty of finding an inclusive definition is 

 correspondingly increased^ 



As a mere word "life" is interesting in 

 the fact that it is one of those abstract 

 terms which has no direct antithesis; al- 

 though probably most persons would re- 

 gard "death" in that light. A little con- 

 sideration will show that this is not the 

 ease. "Death" implies the pre-existenee 

 of "life"; there are physiological grounds 

 for regarding death as a phenomenon of 

 life — it is the completion, the last act of 

 life. We can not speak of a non-living ob- 

 ject as possessing death in the sense that 

 we speak of a living object as possessing 

 life. The adjective "dead" is, it is true, 

 applied in a popular sense antithetically 

 to objects which have never possessed life; 

 as in the proverbial expression "as dead 

 as a door-nail." But in the strict sense 

 such application is not justifiable, since the 

 use of the terms dead and living implies 

 either in the past or in the present the 

 possession of the recognized properties of 

 living matter. On the other hand, the ex- 

 pressions living and lifeless, animate and 

 inanimate, furnish terms which are un- 

 doubtedly antithetical. Strictly and liter- 

 ally, the words animate and inanimate ex- 

 press the presence or absence of "soul"; 

 and not infrequently we find the terms 

 "life" and "soul" erroneously employed 

 as if identical. But it is hardly necessary 

 for me to state that the remarks I have to 

 make regarding "life" must not be taken 

 to apply to the conception to which the 

 word "soul" is attached. The fact that 

 the formation of such a conception is only 

 possible in connection with life, and that 

 the growth and elaboration of the concep- 

 tion has only been possible as the result of 

 the most complex processes of life in the 

 most complex of living organisms, has 

 doubtless led to a belief in the identity of 



life with soul. But unless the use of the 

 expression "soul" is extended to a degree 

 which would deprive it of all special sig- 

 nificance, the distinction between these 

 terms must be strictly maintained. For 

 the problems of life are essentially prob- 

 lems of matter ; we can not conceive of life 

 in the scientific sense as existing apart 

 from matter. The phenomena of life are 

 investigated, and can only be investigated, 

 by the same methods as all other phenom- 

 ena of matter, and the general results of 

 such investigations tend to show that liv- 

 ing beings are governed by laws identical 

 with those which govern inanimate matter. 

 The more we study the manifestations of 

 life the more we become convinced of the 

 truth of this statement and the less we 

 are disposed to call in the aid of a special 

 and unknown form of energy to explain 

 those manifestations. 



The most obvious manifestation of life 

 is "spontaneous" movement. We see a 

 man, a dog, a bird move, and we know 

 that they are alive. We place a drop 

 of pond water under the microscope, 

 and see numberless particles rapidly mov- 

 ing within it; we affirm that it swarms 

 with "life." We notice a small mass of 

 clear slime changing its shape, throwing 

 out projections of its structureless sub- 

 stance, creeping from one part of the field 

 of the microscope to another. We recog- 

 nize that the slime is living; we give it a 

 name — Amceha Umax — the slug amoeba. 

 We observe similar movements in indi- 

 vidual cells of our own body ; in the white 

 corpuscles , of our blood, in connective 

 tissue cells, in growing nerve cells, in 

 young cells everywhere. We denote the 

 similarity between these movements and 

 those of the amoeba by employing the 

 descriptive term "amoeboid" for both. 

 We regard such movements as indica- 

 tive of the possession of "life": nothing 



