54 SCIENCE AND IMMORTALITY 



ground, and they attract other molecules from the 

 air and soil — molecules of carbonic acid, and lime, 

 and potassium, and so on, and lo ! a lily, or a 

 pine tree. Without mistake they carry out their 

 complicated architecture, though there is more 

 machinery in each molecular brick than in a chrono- 

 meter, and more molecular bricks in each leaflet 

 than in a cathedral. 



All living things are built of cells, and cells 

 have a particularly complicated molecular structure. 

 It has been computed that a liver-cell contains 

 300,000000,000000 atoms, of varying size and 

 quality, grouped together in almost infinite variety, 

 into 64,000,000,000 molecules. There is more 

 going on there than in the busiest factory in the 

 world. It has also been computed that the head 

 of a sperm-cell 2^ of a millimetre in diameter 

 contains 2,500,000,000 molecules, each composed 

 of several atoms ; that in a germ-cell there are 

 1,728,000000,000000 molecules, composed of 

 8,640,000,000000,000000 atoms. And all these 

 molecules are marrying, and dancing, and vibrat- 

 ing, and building up some living thing ! It is 

 prodigious ! 



It must be noted that molecules mo\e not only 

 in space, but that they also expand and contract 

 like a beating heart. It is this throbbing or 

 vibrating that causes light. It is the throbbing of 



