THE LIVING MACHINE BUILDING FACTORS. 203 



of cell division with resulting hereditary transmis- 

 sion. For all this we must fall back upon the 

 structure of protoplasm, and say that the cell 

 machinery is so adjusted that the machine, when 

 acting as a whole, is capable of transforming the 

 energy of chemical composition in certain direc- 

 tions. These fundamental properties are then 

 the properties of the cell machine just as surely 

 as printing is the property of the printing press. 

 We can no more account for the life phenomena 

 by chemical powers than we can for printing by 

 chemical forces manifested in the burning of the 

 coal in the engine-room. To be sure, it is the 

 chemical forces in the engine-room that furnishes 

 the energy, but it is the machinery of the press 

 that explains the printing. So, while chemical 

 forces supply life energy, it is the cell machinery 

 that must explain the fundamental living factors. 

 So long as this machine is intact it can continue 

 to run and perform its duties. But it is a very 

 delicate machine, and is easily broken. When it 

 is broken its activities cease. A broken machine 

 cannot run. It is dead. In short, we come back 

 once more to the idea of the machinery of proto- 

 plasm, and must base our understanding of its 

 properties upon its structure. 



It is proper to state that there are still some 

 biologists who insist that the ultimate explanation 

 of protoplasm is purely chemical, and that life 

 phenomena may be manifested in mixtures of 

 compounds that are purely physical mixtures, 

 and not machines. It is claimed that much of 

 this cell structure described above is due to im- 

 perfection in microscopic methods, and does not 



