8 GENERAL BIOLOGY 



conundrum, " What is life ? " so long as we attempt 

 to solve it by processes of analysis, leads us up a 

 blind alley no matter what clue we follow. Yet, 

 in spite of our difficulty in defining living matter, 

 we recognize the existence of it as something real 

 and not imaginary, and when we compare the in- 

 numerable kinds of living things from the standpoint 

 of their physical and chemical composition, we find 

 that they all have much in common ; that life, 

 whatever its metaphysical aspects, has also a mate- 

 rial basis, a " life stuff " or living substance. This 

 living substance has received various names, but 

 that which is most commonly used is Protoplasm. 1 

 This is what Huxley called in enduring phrase " the 

 physical basis of life." 



Chemistry of Protoplasm. In studying the 

 physics and chemistry of protoplasm we find that 

 it is exceedingly complex. But its complexity 

 arises from the almost infinite combinations and 

 permutations of a very limited series of chemical 

 elements. Carbon, hydrogen, oxygen, nitrogen, 

 these we find in all protoplasm, and they constitute 

 its bulk. Sulphur and phosphorus are also always 

 present, but in very much smaller quantities, and 

 usually chlorine, potassium, sodium, magnesium, 

 calcium, and iron as well. Many other elements 

 occur normally, though rarely, in the protoplasm of 

 certain animals and plants. Iodine occurs in sea- 



1 Bioplasm, a term used by many English authors, is perhaps prefer- 

 able, but protoplasm is firmly established in the literature of biologv 



