April 26, 1888] 



NATURE 



619 



in the case of light ? Light exercises its force upon such minute 

 portions of jnatter that until the period of the discovery of 

 photography its physical and chemical effects were almost 

 unknown. Such effects as bleaching, uniting some gases, and 

 affecting the colouring matter of vegetables, were partly known 

 but little attended to ; but photography created a new era : I 

 shall advert to this presently. The theories of light, however, 

 involved matter and motion. The corpuscular theory, as you 

 well know, supposed that excessively small particles were 

 emitted from luminous bodies, and travelled with enormous 

 velocity. The undulatory theory, which supplanted it, supposed 

 that luminous bodies caused undulations or vibrations in a highly 

 tenuous matter called ether, which is supposed to exist through- 

 out the interplanetary spaces and throughout the universe so far 

 as we know it. Some suppose this ether to be of a specific 

 character differing from that of ordinary gases, others that it is 

 in the nature of a highly attenuated gas ; but, whatever it be, it 

 cannot be affected by undulations or vibrations without being 

 moved, and when matter is moved by any force it must offer 

 resistance to that force, and hence we get antagonism between 

 force and resistance. Light also takes time in overcoming this 

 resistance, i.e. in pushing aside the ether. It travels no doubt 

 at a good pace — about 190,000 miles in a second ; but even at this 

 rate, and without being particular as to a few millions of miles, 

 it takes three years and a quarter to reach us from the star 

 which, so far as we know, is the nearest to us, viz. a Cen- 

 tauri. The ether, or whatever it may be called, tenuous as it 

 is, is not unimportant, though it be not heavy. Without it we 

 should have no light and possibly no heat, and the consequences 

 of its absence would be rather formidable. I believe you have 

 heard Dr. Tyndall on this subject. Supposing the visible 

 universe to be as it is now supposed to be, i.e. in no part a mere 

 vacuum, there can be no force without resistance in any part 

 of it. 



But photography carries us further, it shows us that light acts 

 on matter chemically, that it is capable of decomposing or forcing 

 asunder the constituents of chemical compounds, and is there- 

 fore a force met by resistance. In the year 1856 I made some 

 experiments published in the Philosophical Magazine for January 

 1857, which seemed to me to carry still further what I may call the 

 molecular fight between light and chemical affinity, and among 

 them the following. Letters cut out of paper are placed 

 between two polished squares of glass with tin-foil on the out- 

 sides. It is then electrized like a Leyden jar, for a few seconds, 

 the glasses separated, the letters blown off, and the inside of one 

 of the glasses covered with jDhotographic collodion. This is then 

 exposed to diffuse daylight, and on being immersed in the nitrate 

 of silver bath the part which had been covered with the paper 

 comes out dark, the remainder of the plate being unaffected. 

 (This result was shown by the electric light lantern.) In this 

 case we see that another imponderable force, electricity, invisibly 

 affects the surface of glass in such a way that it conveys to 

 another substance of definite thickness, viz. the prepared 

 collodion, a change in the chemical relations of the substance 

 (iodide of silver) pervading it, enabling it to resist that de- 

 composition by light which but for some unseen modification of 

 the surface of the glass plate it would have undergone, and no 

 doubt the force of light being unable to effect its object was 

 reflected or dispersed, and instead of changing its mode of 

 motion in effecting chemical decomposition, it goes off on 

 other business. The visible effect is in the collodion film alone. 

 I have stripped that ofit', and the imprint remains on it, the surface 

 of the glass being, so far as I could ascertain, unaffected. Thus 

 in the film over the protected part, light conquers chemical 

 affinity ; in that over the non-protected part, chemical affinity 

 resists and conquers light, which has to make an ignominious 

 retreat. It is a curious chapter in the history of the struggles 

 of molecular forces, and probably similar contests between light 

 and chemical or physical attractions go on in many natural 

 phenomena, some forms of blight and some healthy vegetable 

 changes being probably dependent on the varying effects of light, 

 and conditions, electrical or otherwise, of the atmosphere. 



Let us now pass on to organic life. A blade of grass, as 

 Ikirke, I believe, said as a figure of speech, is fighting with its 

 neighbours. It is robbing them, and they are trying to rob it- 

 no agreement or contract, simply force opposed to force. This 

 struggle is good for the grass ; if it got too much nutriment it 

 would become diseased. The struggle keeps it in health. The 

 rising of sap in trees, the assimilation of carbon, the process of 

 growth, the strengthening themselves to resist prevalent winds, 



and many other instances might be given, which afford examples 

 of the internal and external struggles in vegetable life. 



I will now proceed to consider animal life, and in this case I will 

 begin with the internal life of animals, which is a continual 

 struggle. That great pump the heart is continuously beating — 

 that is, conquering resistance. It is forcing the blood through 

 the arteries, they assisting in squeezing it onwards. If they give 

 way the animal dies ; if they become rigid and resist too much, 

 the animal dies. There must be a regulated antagonism, a 

 rhythmical pulsation, the very term involving force and resist- 

 ance. That the act of breathing is antagonistic scarcely needs 

 argument. The muscular action by which the ribs are made to 

 open out and close alternately, in order to inhale and exhale air, 

 and other physiological changes which I cannot here go into, 

 necessitate a continuous fight for life. So with digestion, assimi- 

 lation, and other functions, mechanical and chemical forces and 

 resistances come into play. 



Since this lecture was written, I have heard of a discovery 

 made, I am informed, by Prof. Metschnikoff, and which has 

 brought to light a singular instance of internal antagonism. 

 He is said to have proved that the white corpuscles of the 

 blood are permanent enemies of Bacteria, and by inoculation wiU 

 absorb poisonous germs ; a recurrent war, as it appears, going 

 on between them. If the corpuscle is the conqueror, the Bacteria 

 are swallowed up, and the patient lives. If the corpuscles are 

 vanquished, the patient dies, and the Bacteria live, at all events for 

 a time. If the theory is founded, it affords a strong additional 

 argument to the doctrine of internal antagonism. Possibly if 

 there were no Bacteria, and the corpuscles had nothing to do, it 

 would be worse for them and the animal whom they serve. 



Let us now consider the external life of animals. I will take as 

 an instance, for a reason which you will soon see, the life of a 

 wild rabbit. It is throughout its life, except when asleep (of 

 which more presently), using exertion, cropping grass, at war with 

 vegetables, &c. If it gets a luxurious pasture it dies of repletion. 

 If it gets too little it dies of inanition. To keep itself healthy 

 it must exert itself for its food ; this, and perhaps the avoiding its 

 enemies, gives it exercise and care, brings all its organs into use, 

 and thus it acquires its most perfect form of life. I have wit- 

 nessed this effect myself, and that is the reason why I choose 

 the rabbit as an example. An estate in Somersetshire, which I 

 once took temporarily, was on the slope of the Mendip Hills. 

 The rabbits on one part of it, viz. that on the hill-side, 

 were in perfect condition, not too fat nor too thin, sleek, active, 

 and vigorous, and yielding to their antagonists, myself and family, 

 excellent food. Those in the valley, where the pasturage was rich 

 and luxuriant, were all diseased, most of them unfit for human 

 food and many lying dead on the fields. They had not to 

 struggle for life, their short life was miserable and their death 

 early, they wanted the sweet uses of adversity — that is, of 

 antagonism. 



The same story may be told of other animals. Carnivora, 

 beasts or birds of prey, live on weaker animals ; weaker animals 

 herd together to resist, or, by better chance of warning, to escape, 

 beasts of prey ; while they, the Herbivora, in their turn are 

 destroying vegetable organisms. 



I now come to the most delicate part of my subject, viz. man 

 (I include women of course !). Is man exempt from this continual 

 struggle? 



It is needless to say that war is antagonism. Is not peace sa 

 also, though in a different form ? It is a common-place remark 

 to say that the idle man is worn out by etiitui, i.e. by internal 

 antagonism, Kingsley's " Do-as-you-like " race— who were fed 

 by a substance dropping from trees, who did no work, and who 

 gradually degenerated until they became inferior to apes, and 

 ultimately died out from having nothing to do, nothing to 

 struggle with— is a caricature illustrative of the matter. That the 

 worry of competition is nearly equivalent to the hardships and 

 perils of military life seems proved to me by the rea,diness with 

 which military life is voluntarily undertaken, ill as it is paid. If 

 it were well paid, half our men would be in the military or 

 naval service, and I am not sure that we should not have regiments 

 of Amazons ! The increased risk of life or limbs and the arduous 

 nature of the work do not prevent men belonging to all classes 

 from entering these services, little remunerative as they are. 

 Others take the risks of travelling in the deserts of Africa or 

 wintering in the Polar regions, of being eaten by lions or frozen to 

 death, of falling from a Swiss mountain or foundering in a yacht, 

 in preference to a life of tranquillity ; and sportsmen elect the- 

 danger of endeavouring to kill an animal that can and may kilt 



