338 



SCIENCE 



[N. S. Vol. XXXVIII. No. 975 



the distin^ishing characteristics of the 

 living organism. All organisms are primar- 

 ily complex, i. e., the number of dis- 

 tinguishable structural and functional com- 

 ponents is large; they are the seat of con- 

 tinued chemical change involving constant 

 interchange of matter and energy with the en- 

 vironment — in a word,, of metabolism; and 

 they exhibit durability or stability in an en- 

 vironment more or less subject to change; in 

 other words, the possession of an automatic 

 power of adjustment to changing conditions, 

 or of regulation, is typically highly developed. 

 Complexity, regulation and an energy-yield- 

 ing metabolism are thus essential to organ- 

 isms. The question is then asked : " To what 

 extent do the characteristics of matter and 

 energy and the cosmic processes favor the ex- 

 istence of mechanisms which must be complex, 

 highly regulated, and provided with suitable 

 matter and energy as food ? " 



By a process of elimination the author de- 

 fines water and carbon dioxide as those con- 

 stituents of the environment which are most 

 essential to life. The physico-chemical pecu- 

 liarities of these two substances are then con- 

 sidered at length. The remarkable solvent, 

 thermal and dielectric properties of water are 

 shown to be indispensable to the complexity 

 and stability of living protoplasm; the im- 

 portance of its chemical properties, especially 

 its ionizing and hydrolyzing action, is also 

 dwelt upon. Similarly, the many remarkable 

 properties of carbon dioxide are pointed out, 

 in particular, its high solubility — a necessary 

 condition for enabling organisms to utilize it 

 in such large quantity — and its dissociation- 

 constant, which has just the value that is niost 

 favorable to the preservation of an approxi- 

 mate neutrality in aqueous solutions contain- 

 ing its salts: protoplasm is thus protected 

 against wide variation in its hydrogen-ion con- 

 centration; the constancy of reaction thus 

 secured is a highly important factor in secur- 

 ing constancy of chemical conditions in cells, 

 and hence in furnishing the conditions for a 

 stable chemical organization. Other important 

 constituents of the environment are salts: the 

 abundance and variety of these in. sea-water 



are pointed out, and their importance in vital 

 processes — depending largely on their charac- 

 teristic relations to the colloids — is empha- 

 sized. Water, carbon dioxide and salts are 

 thus the essential constituents of the environ- 

 ment of living organisms, and it is ultimately 

 from these substances that the living matter 

 is synthesized. In correspondence with the 

 importance assigned to these substances, spe- 

 cial chapters are devoted to water, carbon 

 dioxide and the ocean. The properties of sub- 

 stances in a state of solution are also discussed 

 (osmotic pressure, diffusion, ionization). The 

 following chapter reviews the chief features 

 in the chemical behavior of the three chief 

 elements and their compounds. The author 

 insists that carbon alone, of all the elements, 

 has the properties which render possible the 

 formation of compounds sufficient in number, 

 kind and complexity for vital processes. He 

 also calls especial attention to the mobility of 

 carbon — due to the gaseous nature and high 

 solubility of its oxide — and to the importance 

 of the high heat combustion of carbon and 

 hydrogen and their compounds in the ener- 

 getics of vital processes. By simple reduction, 

 followed by polymerization, carbonic acid 

 passes over into the sugars; and thus the first 

 step from the simple gaseous oxide to complex 

 organic substances, which at the same time are 

 reservoirs of energy, is remarkably simple and 

 direct. The close chemical affiliations of the 

 sugars to niany other compounds important to 

 the organism are also briefly discussed. This 

 part of the book is itself a concise summary 

 and hence can not be satisfactorily summar- 

 ized. The author's essential conclusion is that 

 the foregoing characteristics of carbon, hydro- 

 gen and oxygen, which make possible the pro- 

 duction of living protoplasm, constitute a 

 series of maxima — are unique when compared 

 with the corresponding properties of other ele- 

 ments. Hence they show the greatest possible 

 fitness for life. 



In Chapter 7 the argument is restated in 

 more concise form, and in the final chapter, 

 "Life and the Cosmos," the possible signifi- 

 cance of living beings in the whole scheme of 

 nature is considered. How comes it that the 



