CHARACTERISTICS OF LIVING .MATTER 3 



organization of these compounds in new structural and 

 chemical relationships, constitute the fundamental activi- 

 ties of all living matter. Hence a consideration of 

 the general features of metabolic processes must come 

 first in any discussion of the nature of protoplasmic 

 action. 



Under the term metabolism are included primarily 

 the nutritive and energy-yielding chemical processes in 

 protoplasm, and secondarily the other chemical processes 

 subserving or underlying these. The application of the 

 term is usually clear; but metabolic processes comprise 

 chemical reactions of all kinds, many of which are in no 

 sense peculiar to organisms, while others are not met 

 with elsewhere in nature. The traditional distinction 

 between constructive and destructive metabolism remains 

 an essential one; what the organism is at any time is a 

 resultant of the effects of these two large and, in general, 

 oppositely directed groups of chemical reactions. 

 Broadly speaking, the constructive reactions represent 

 the nutritive processes, and the destructive reactions 

 the energy-yielding processes. Constructive metabolism 

 includes the synthetic (anabolic) reactions underlying 

 growth, self-maintenance, and reproduction. In any 

 species the end-products of the constructive sequence of 

 reactions consist largely of certain colloidal compounds, 

 highly individualized and specific in their chemical 

 constitution, the proteins; the other synthetic products 

 (carbohydrates, fats, lipoids, etc.) are chemically non- 

 specific; i.e., not confined to the species in question; 

 these form, together with the specific compounds, water 

 and various dissolved substances, a complex and highly 

 organized system, or organic individual, wliich is specific 



