42 WHAT IS LIFE 



lisation, to point out that some living organisms 

 do construct crystals within themselves so that if 

 the parallel between crystallisation and assimilation 

 were a fair one we should be confronted with the 

 somewhat bizarre fact that one kind of crystallisa- 

 tion was making use of another for its own 

 purposes. 



Living The facts, however, which have been brought 



forward by Professor Minchin l show not only how 

 different the two processes are but also how the 

 living cell is able to modify the process of natural 

 crystallisation for its own purposes. He says : 

 " An ordinary crystal owes its peculiar character- 

 istics entirely to the action of the laws of inorganic 

 matter, laws which admit of being accurately 

 formulated and accurately calculated. Crystalline 

 bodies are, however, known to occur which have 

 been deposited within living bodies, and which 

 owe their origin to vital activities. In such cases, 

 the crystals, while identical in their chemical com- 

 position and molecular structure with crystals of 

 inorganic origin, may exhibit, at the same time, 

 certain peculiarities which are due entirely to the 

 circumstances of their origin. . . . The relation 

 of the spicules to the structure of the sponge shows 

 that they have a definite function to perform and 

 an important part to play in the economy of the 

 1 " Living Crystals/' Proc. Boy. Inst., vol. xv. 



