ANTAGONISM. 613 



chemical relations of the substance (iodide of silver) pervading it, 

 enabling it to resist that decomposition 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 off, 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 afiinity 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 prob- 

 ably 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 Burke, 

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

 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 ex- 

 ternal 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 onward. 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 can not here go into, ne- 

 cessitate a continuous fight for life. So with digestion, assimila- 

 tion, and other functions, mechanical and chemical forces and re- 

 sistances 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 



