NEWEST IDEAS AS TO WHAT IS LIFE 



an estimate of how many co-operating units are repre- 

 sented in the activities of a single liver-cell. The latter 

 ranges in size from seventy-five to one hundred cubic mi- 

 crons (75-100 /**). As the micron is about the twenty- 

 five thousandth of an inch, a cubic inch of liver contains, 

 then, around 156,000 million cells. As the human liver 

 contains about 90 cubic inches, it will be seen that it is a 

 rather complex body, at least in point of numbers. 



Nevertheless, although these minute cells are invisible 

 to the naked eye, they are perfectly visible and open to 

 study under the microscope. They are made up, like all 

 other cells, of a nucleus or kernel, and a surrounding mass 

 of semiliquid substance. The whole cell assumes a gran- 

 ular appearance under high magnification. 



Probably, like living matter in general, they average 

 about one-fifth solid substance, the rest being water; but 

 this water is incorporated as an integral part of the living 

 molecule. Gautier and others estimate that the white-of- 

 egg molecule contains five or six thousand atoms. Ws 

 have seen, in the chapter on "What This World Is Made 

 of," that the average molecule in a gas is about one-fifth 

 of a micro-micron in diameter (0.2 /*/*), so if each of these 

 gaseous molecules contains two atoms, we may take one- 

 tenth of a micro-micron (o.i j*/i) as the average atomic 

 diameter. 



Of course this is only the roughest sort of a figure, but 

 the actual size is probably not more than five or ten times 

 more or less than this. On this basis, the albumen mole- 

 cule, containing five thousand atoms of carbon, hydrogen, 

 nitrogen, and oxygen, might be somewhere around one and 

 three-quarter micro-microns (1.75 /*/*) in diameter. It is 

 probable that the living molecule is rather larger than 

 this, but we have as yet no means of knowing. I will take 

 this figure provisionally. If the size of the liver-cell is 

 from seventy-five to one hundred cubic microns, its diam- 

 eter will be around seven microns (7 /i), or four thousand 

 times the diameter assumed for the albumen molecule. 



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