ON THE MYSTERY OF LIFE. 659 



EVENING DISCOURSE. 



THE MYSTERY OF LIFE. 



By Prof. F. G. Donnan, F.R.S. 



DuKiNG the last forty years the sciences of physics and chemistry have made 

 tremendous strides. The physico-chemical world has been analysed into three 

 components — electrons, protons and the electro-magnetic field with its streams of 

 radiant energy. Concurrently with these advances astronomy has progressed to 

 an extent undreamed of forty years ago. The distances, sizes, masses, temperatures, 

 and even the constitutions of far-distant stars have been ascertained and compared. 

 The evolution of the almost inconceivably distant nebulae and their condensation 

 into stars and star clusters have been unravelled with a skill and knowledge that 

 would have been deemed superhuman a hundred years ago. Amidst the vast cosmos 

 thus disclosed to the mind of man, our sun winds its modest way, an unimportant 

 star, old in years and approaching death. Once upon a time, so the astronomers tell 

 us, its surface was rippled by the gravitational pull of a passing star, and the ripples 

 becoming waves, broke and splashed off. Some drops of this glowing spray, held by 

 the sun's attraction in revolving orbits, cooled down and became the planets of our 

 solar system. Our own planet, the earth, gradually acquired a solid crust. Then 

 the water vapour in its atmosphere began to condense, and produced oceans, lakes 

 and rivers as the temperature sank. It is probably at leiat a thousand million years 

 since the earth acquired a solid crust of rock. During that period living beings, plants 

 and animals, have appeared, and, as the story of the rocks tells us, have developed by 

 degrees from small and lowly ancestors. The last product of this development is 

 the mind of man. What a strange story ! On the cool surface of this little planet, 

 warmed by the rays of a declining star, stands the small company of life. One with 

 the green meadows and the flowers, the birds and the fishes and the beasts, man 

 with all his kith and kin counts for but an infinitesimal fraction of the surface of the 

 earth, and yet it is the mind of man that has penetrated the cosmos and discovered 

 the distant stars and nebulae. Truly we may say that life is the great mystery and 

 the study of life the greatest study of all. The understanding of the phenomena of 

 life will surely be the crowning glory of science, towards which all our present chemical 

 and physical knowledge forms but the preliminary steps. 



Observing the apparent freedom, spontaneity and indeed waywardness of many 

 forms of life, we are at first lost in amazement. Is this thing we call life some strange 

 and magical intruder, some source of lawless and spontaneous action, some fallen 

 angel from an unknown and inconceivable universe ? That is indeed the question 

 we have to examine, and we may begin our examination in a general way by inquiring 

 whether living things are subject to the laws of energy that control the mass phenomena 

 of the inanimate world. The first of these laws, known as the law of the Conservation 

 of Energy, says that work or energy can only be produced at the expense of some 

 other form, and that there are definite rates of equivalence or exchange between the 

 appearing and disappearing forms of energy. In a closed system we can make up 

 a balance sheet, and we find that the algebraic sum of the increases and decreases, 

 allowing, of course, for the fixed rates of exchange, is zero. That was one of the 

 great discoveries of the nineteenth century. The physiologists have found that 

 living beings form no exception to this law. If we put a guinea-pig or a man 

 into a nutrition calorimeter, measure the work and heat produced and the energy 

 values of the food taken in and the materials given out, we find our balance 

 sheet correct. The living being neither destroys nor creates energy. One part of 

 the apparent freedom or spontaneity of which I spoke is gone. Energy-producing 

 action must be paid for by energy consumed. The living being does not break the 

 rules of exchange that govern the markets of the non-living and the dead. Another 

 great discovery of the nineteenth century, the so-called Second Law of Thermo- 



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