LIFE, ITS PHYSICAL . BASIS AND SIMPLEST EXPHi:SSIO\ 27 



plasmic stuff representing these two conditions must !)e disposed 

 in certain definite relations. Protoplasm nuist occur as a cell 

 or cells to be capable of performing the necessary activities of 

 life. Hence we must consider at the very begimiing of any dis- 

 cussion of life the two things, protoplasm and the cell. 



The elements tiiat compose protoplasm are the familiar ones, 

 carbon, nitrogen, h3Tlrogen, oxygen, sulphur, phosphorus, 

 potassium, sodium, etc.; but these elements, or some of them, 

 are found in protoplasmic cells in certain comj)lex combiiialion.s 

 which arc not found elsewhere in nature, and which thcrcfon! 

 actually and absolutely distinguish chemically living proto- 

 plasm from all lifeless matter. These particular com))inations 

 are certain albuminous compounds or proteids, comj)os('d of 

 C, H, O, N, and S, and their complexity is extreme: the atoms 

 in a single molecule often number more than a thousand. The 

 molecules also are very large, which is proljably the reason of 

 their characteristic nondiffusibility through animal membranes 

 or artificial parchment. 



In addition to these characteristic all)uminous compounds 

 and various derivatives of them, proto])lasm usual' y contains 

 certain native albumins and certain other characteristic com- 

 pounds known as carbohydrates and fats (wliich differ essen- 

 tially from the albuminous substances in lacking nitrogen as a 

 composing element). There are also various salts and gases 

 and alwavs water to be found in Uving substances, ^^'ate^ is 

 absolutely necessary to the physical condition of half fluidity 

 which gives to protoplasm its essential capacity for motion on 

 itfc^lf. The commoner salts found in hving substances are 

 compounds of chlorine as well as the carbonates, suli)hates, and 

 phosphates of the alkalies and alkali earths, especially conunon 

 salt (sodium chloride), potassium chloride, annnoniiun chh^nde, 

 and the carbonates, sulphides, and suli)hates of sodium, jwtjis- 

 sium, magnesium, ammonium, and calcium. The gases found 

 in Uving matter are oxygen and car])on dioxide. Tlics' . when 

 not in chemical combination, are almost always dissolved in 

 water, although rarely they may be in the Umn of gas hubblrs. 



To sum up the relation of living matter to chemistry we may 

 say that life is always associated with jirotoplasm. and that this 

 protoplasm is made up of a few familiar inorganic elements, 

 particularly those of lowest atomic weight; that it does not 

 include any special so-called vital or life element, that is. any 



