ON THE MYSTERY OF LIFE. 663 



tion of the various organs and tissues of a living organism over confronts us as one of 

 the great mysteries of life. In an inanimate physico-chemical system wo thiitk, if 

 we know the situations, modes of action and interrelations of the component parts, 

 whether particles or waves (or both), together with the boundary conditions of the 

 system, that we have effected a complete synthesis of the whole. Though very 

 crudely expressed, some such view as that lies at the basis of the Newtonian philosophy 

 which rules our thought in the inanimate physico-chemical world. Is the organised 

 djTiamical unity of a living organism something fundamentally new and different ? 

 Confronted by a problem of this order of difficulty, it behoves us to be patient and 

 to await the future progress of scientific research. Perhaps if we could actually -witness 

 and follow out the varied motions and activities of a single complex chemical molecule 

 in a reacting medium we might find something not so very different from life. Or 

 perhaps the organic unity of a living organism requires for its understanding some 

 such explosion of human thought and inspiration as that which occuiTed when Einstein 

 and Minkowsky discovered the true relations of what we call space and time. We may, 

 however, be sure of this. The understanding, when it comes, will consist in something 

 that permits of exact measurement and of precise expression in mathematical form, 

 even though for the latter purpose a new form of mathematics may have to be invented. 



Leibnitz once remarked that ' the machmes of nature, that is to say, living bodies, 

 are still machines in their smallest parts ad ivfinituvi.' Anatomy and histology have 

 progressively disclosed the structure of living things. Histology has revealed to us 

 the cell with its nucleus and cytoplasm as the apparently fundamental unit of all 

 the organs and tissues of a living being. What is contained within the membrane of 

 a living cell ? Here we approach the inner citadel of the mystery of life. If we can 

 analyse and understand this, the first great problem — perhaps the only real problem — 

 of general phj^siology will have been solved. The study of the nature and behaviour 

 of the living cell and of unicellular organisms is the true task of biology to-day. 



The living cell contains a system known as protoplasm, though as yet no one 

 can define what protoplasm is. One of the fundamental components of this system 

 is the class of chemical substances known as proteins, and each type of cell in each 

 species of organism contains one or more proteins which are peculiar to it. Important 

 components of the protoplasmic system are water and the chlorides, bicarbonates 

 and phosphates of sodium, potassium and calcium. Other substances are also 

 present, especially those mysterious bodies known as enzymes, which catalyse the 

 various chemical actions occurring within the cell. Strange to say, the living cell 

 contains within itself the seeds of death, namely those so-called autolytic enzymes, 

 which are capable of hydi-olysing and breaking down the protein components of the 

 protoplasm. So long, however, as the cell continues to live, these autolytic enzymes 

 do not act. What a strange thing ! The harpies of death sleep in every unit of our 

 living bodies, but as long as life is there their wings are bound and their devouring 

 mouths are closed. 



This protoplasmic system exists in what is known as the colloid state. Roughly 

 speaking, this means that it exists as a rather fluid sort of jelly. There is something 

 extraordinarily significant in this colloid state of the protoplasmic system, though 

 no one as yet can say what it really means. Recollecting the statement of Leibnitz, 

 one may be sure that the protoplasmic system of the cell constitutes a wonderful 

 sort of machine. There must exist some very curious inner structure where the 

 protein molecules are marshalled and arrayed as long mobile chains or columns. 

 The molecular army within the cell is ready for quick and organised action and is 

 in a state, during life, of constant activity. Oxidation, assimilation and the rejection 

 of waste products are always going on. The living cell is constantly exchanging 

 energy and materials with its environment. The apparently stationary equilibrium 

 is in reality a kinetic or dynamic equilibrium. But there is a great mystery here. 

 Deprive your motor car of petrol or of oxygen and the engine stops. Yes, but it 

 doesn't die, it does not begin at once to go to pieces. Deprive the living cell of oxygen 

 or food and it dies and begins at once to go to pieces. The autolytic enzyines begin 

 to hydrolyse and break down the dead protoplasm. Why is this ? What is cellular 

 death ? The atoms and the molecules and ions are still there. Meyerhof has shoMTi 

 that the energy content of living protein is no greater than that of dead protein. Has 

 some ghostly entelechy or vital impulse escaped unobserved ? Now it is just here, 

 at the very'gate between life and death, that the English physiologist, A. V. Hill, 

 is on the eve of a discoverj' of astounding importance, if indeed he has not already 

 made it. It appears from his work on non-medullated nerve cells and on muscle 



