MACROMOLECULAR COMPLEXES 

 84 



Neither the physical nor the biological factors controlling crystal growth 

 are well enough known to answer the second part of your question. It may be 

 of interest, however, that the apatite crystals in the enamel of tooth are very 

 much larger than those in the adjacent dentin. Presumably, part of this may 

 be due to rates of crystal growth; i.e., the slower the rate, the larger and more 

 perfect the crystals. I have been told that the "spikes" of certain sea urchins 

 which are 7 inches or longer are composed of a single crystal of calcite. 



