THE BIOLOGY OF THE CELL SURFACE 



weight and size. The classification of living things, the 

 earliest scientific treatment of life, relies upon measure- 

 ments. The anatomist, be he interested in bones or in 

 chromosomes, reckons size and number. These kinds of 

 simple and direct measuring have a definite place in biology. 

 Similarly have those relating to the functions of the living 

 thing. No one questions the value of measurement for the 

 analysis of the gases in human blood. He who would be 

 foolhardy enough to deny the dependence of biology upon 

 physics and chemistry would do well to ponder the history 

 of the research on animal respiration, beginning with 

 Lavoisier, whose work stands as a new starting point for 

 both chemistry and biology. The final proof that the blood 

 carries most of its contained oxygen in chemical rather than 

 in physical union constitutes one of the most brilliant chap- 

 ters in biology to read which quickens the pulse. The 

 measurements on temperature, on pressure, of electrical 

 conditions, of light, of the chemical breaking down of com- 

 plex foods and the building up of these, the photosynthetic 

 process in green plants without which human life would 

 become immediately impossible — these and many others 

 show that biology comprises a welter of physico-chemical 

 measurements, a fact to occasion no astonishment since 

 living things are physico-chemical entities. 



The measurements employed in physical science which 

 do not apply to living things concern states of matter below 

 that level of organization which characterizes a living thing. 

 True, matter in the living state as all matter is compounded 

 of electrons. The high and enviable excellence of modern 

 physics rests upon the beautiful and enthralling analysis 

 of the ultimate unit-structure of the least particle of which 

 all nature is composed. However, the fact that life as far 

 as we know exists as a composite, and only as such, 

 renders pure physical analysis, i.e., into electrons, inappli- 

 cable to the state of being alive. I'he fact that life dissolves 



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