192 



ANIMAL BIOLOGY. 



[Part I. 



and descending steps, which together form a pyramid. The 

 summit of that pyramid is protoplasm, which the student must 

 not regard as a body of unchanging chemical composition, but 

 rather as a group of bodies, each the terminal product of a 

 series of anabolic processes. It is scarcely probable that the 

 protoplasm of muscle, nerve, and glandular tissue is identical. 

 But in each case it is the highest product of a special line of 

 anabolism. And in general we may say that protoplasm is the 

 summit of a step-faced metabolic pyramid. The ascending steps 

 are anastates ; the descending steps katastates. The ascent of 

 the pyramid involves the absorption of energy or work done 

 on the matter involved. The descent of the pyramid involves 

 the setting free of energy, in the form of visible motion or of 

 heat, or work done by the matter involved. But the pyramid 



Living 

 Protoplasm. 



Anabolic 

 Mesostates. 



Katabolic 

 Mesostates. 



FIG. 58. METABOLIC LIFE-PYRAMID. 



is not symmetrical. Its katastatic side, with descending steps, 

 is longer than its anastatic side with ascending steps ; for the 

 food starts at a higher level of energy and complexity than that 



