SCIENCE. 



229 



faculty of appropriating foreign substances into its own, 

 making them subservient to the renewal of its own material, 

 to the maintenance of its own energy, and to the preserva- 

 tion of its own separate individuality. It has the faculty, 

 moreover, of giving off parts of itself, endowed with the 

 same properties, to lead a separate existence. This same 

 substance, which when analyzed has always the same 

 chemical composition, and when alive has always the same 

 fundamental properties, is at the root of every organism, 

 whether animal or vegetable. Out of its material all visible 

 structure is 1 uilt up, and the power which holds its ele- 

 ments together is the same power which performs the 

 further work of molding them into tissues — first forming 

 them, and then feeding them, and then keeping them in 

 life. This is as true of the highest organism of Man as it is 

 of the lowest, in which visible structure begins to be. The 

 phenomena of disease have convinced physiologists that all 

 the tissues of the body are freely penetrated by the proto- 

 plasmic corpuscles of the blood, and that the primordial 

 properties displayed in the substance of an Amoeba, which 

 has no distinguishable parts and no separate organs, afford 

 the only key to the fundamental properties of every animal 

 body. One eminent observer assigns so high a place to 

 this protoplasmic matter as the primary physical agent in 

 the building of the House of Life, and in its renovation 

 and repair, that he considers all its other materials, and all 

 its completed structures as comparatively " dead." 



But the unity of Man's body with the rest of Nature lies 

 deeper still than this. The same elements and the same 

 primary compounds are but the foundations from which the 

 higher unities arise. These higher unities appear to depend 

 upon and to be explained by this — that theie are certain 

 things which must be done for the support of animal life, 

 and these things are fundamentally the same from the low- 

 est to the highest creatures. It is for the doing of these 

 things that " organs " are required, and it is in response to 

 this requirement that they are provided. Food — that is to 

 say, foreign material — must be taken in, and it must be as- 

 similated. The circulating fluids of the body must absorb 

 oxygen ; and when this cannot be done more simply, a 

 special apparatus must be provided for the separation of 

 this essential element of life from the air or from the water. 

 Sensation must be localized and adapted to the perception 

 of movements in surrounding media. The tremors of the 

 atmosphere and of the luminiferous ether must first be 

 caught upon responsive — that is to say, upon adapted — 

 surfaces, and then they must be translated into the language 

 of sensation — that is to say, into sight and hearing. The heat 

 evolved in the chemical processes of digestion and of oxygen- 

 ation of the blood must be made convertible into other forms 

 of motion. The forces thus concentrated must be stored, 

 rendered accessible to the Will, and distributed to members 

 which are at its command. These and and many other 

 uniform necessities of the animal frame constitute a unity 

 of function in organs of the widest dissimilarity of form, so 

 that however different they may be in shape, or in structure, 

 or in position, they are all obviously reducible to one com- 

 mon interpretation. They do the same things — they serve 

 the same purposes — they secure the same ends — or, to use 

 the language of physiology, they discharge the same func- 

 tions in the animal economy. 



But more than this ; even the differences of form steadily 

 diminish as we ascend in the scale of being. Not only are 

 the same functions discharged, but they are discharged by 

 organs of the same general shape, formed on one pattern, 

 and occupying an identical position in one plan of structure. 

 It is on this fact that this science of comparative anatomy 

 is founded, and the well-established doctrine of " homolo- 

 gies." The homology of two organs in two separate animals 

 is nothing but the unity of place which they occupy in a 

 structure which is recognized as one and the same in a vast 

 variety of creatures — a structure which is one in its general 

 conception, and one in the relative arrangement of its 

 parts. In this clear and very definite sense, the body of 

 Man, as a whole, is one in structure with the bodies of all 

 vertebrate animals ; and as we rise from the lowest of these 

 to him who is the highest, we see that same structure ela- 

 borated into closer and closer likeness, until every part 

 corresponds — bone to bone, tissue to tissue, organ to organ. 

 It is round this fact that so many disputants are now fight- 

 ing. But all the controversy arises, not as to the existence 



of the fact, but as to its physical cause. The fact is beyond 

 question. In a former work 2 I have dwelt at some length 

 on the bearing of this fact on our conceptions of" Creation 

 by Law," and on the various theories which assume that 

 such close relationshio in organic structure can be due to 

 no other cause than blood relationship through ordinary 

 generation. At present I am only concerned with the fact 

 of unity, whatever may be the physical cause from which 

 that unity has arisen. The significance of it, as establishing 

 Man's place in the unity of Nature, is altogether independ- 

 ent of any conclusion which maybe reached as to those 

 processes of creation by which his body has been fashioned 

 on a plan which is common to him and to so many animals 

 beneath him. Whether Man has been separately created 

 out of the inorganic elements of which his body is com- 

 posed, or whether it was born of matter previously organ- 

 ized in lower forms, this community of structure must 

 equally indicate- a corresponding community of relations 

 with external things, and some antecedent necessity deeply 

 seated in the very nature of those things, why his bodily 

 frame should be like to theirs. 



And, indeed, when we consider the matter, it is sufficiently 

 apparent that the relationship of Man's body to the bodies of 

 the lower animals is only a subordinate part and consequence 

 of that higher and more general relationship which prevails 

 between all living things and those elementary forces of 

 Nature which play in them, and around them, and upon 

 them. If we could only know what that relationship is in 

 its real nature and in its full extent, we should know one of 

 the most inscrutable of all secrets. For that secret is no 

 other than the ultimate nature of Life. The great matter is 

 to keep the little knowledge of it which we possess safe from 

 the confusing effect of deceptive definitions. The real uni- 

 ties of Nature will never be reached by confounding her 

 distinctions. For certain purposes it may be a legitimate 

 attempt to reduce the definition of Life to its lowest terms — 

 that is to say, it may be legitimate to fix our attention ex- 

 clusively on those characteristics which are common to Life 

 in its lowest and in its highest forms, and to set aside all 

 other characteristics in which they differ. It may be useful 

 sometimes to look at Life under the terms of such a defini- 

 tion, in order, for example, the better to conceive some of 

 its relations with other things. But in doing so we must 

 take care not to drop out of the terms so defining Life any- 

 thing really essential to the very idea of it. Artificial defini- 

 tions of this kind are dangerous experiments in philosophy. 

 It is very easy by mere artifices of language to obliterate the 

 most absolute distinctions which exist in Nature. Between 

 the living and the non-living there is a great gulf fixed, and 

 the indissoluble connection which somehow, nevertheless, 

 we know to exist between them is a connection which does 

 not fill up that gulf, but is kept up by somebiidge being, as 

 it were, artificially built across it. This unity, like the other 

 unities of Nature, is not a unity consisting of mere contin- 

 uity of substance. It is not founded upon sameness, but, 

 on the contrary, rather upon difference, and even upon an- 

 tagonisms. Only the forces which are thus different and 

 opposed are subordinate to a system of adaptation and ad- 

 justment. Nor must we fail to notice the kind of unity 

 which is implied in the very words " adaptation " and " ad- 

 justment " — and, above all others, in the special adjustments 

 connected with organic Life. There are many unions which 

 do not involve the idea of adjustment, or which involve it 

 only in the most rudimentary form. The mere chemical 

 union of two or more elements — unless under special con- 

 ditions — is not properly an adjustment. We should not 

 naturally call the formation of rust an adjustment between 

 the oxygen of the atmosphere and metallic iron. When 

 the combinations effected by the play of chemical affi- 

 nities are brought about by the selection of elements 

 so placed within reach of each other's reactions as to 

 result in a given product, then that product would 

 be accurately described as the result of co-ordination 

 and adjustment. But the kind of co-ordination and 

 adjustment which appears in the facts of Life is of a still 

 higher and more complicated kind than this. Whatever 

 the relationship may be between living organisms and the 

 elements, or elementary forces of external Nature, it cer- 

 tainly is not the relationship of mere chemical affinities. On 



s " The Reign of Law." 



