ZOOLOGY. 



THE INVERTEBRATA. 



INTRODUCTORY. 



What is Protoplasm ? 



Living matter ; or, as Huxley termed it, " the physical 

 basis of life." It is glutinous and usually somewhat fluid. 

 Chemically it consists of a very complex substance known 

 as protein, which is mainly composed of carbon, nitrogen, 

 oxygen, hydrogen, sulphur, with phosphorus and other 

 elements in combination. 



Living protoplasm exhibits ceaseless change. There is 

 a continual slow combustion ; oxygen is taken in and 

 combined with carbon and given off as carbon dioxide ; 

 food material is absorbed, elaborated, and assimilated. 

 Concurrently with the building up (anabolism) there is 

 the breaking down (katabolism) into non-living matter 

 or wastes. The whole process is termed metabolism, and 

 to its resultant energies movement and other visible mani- 

 festations of life are attributable. 



Contrast Anabolism and Katabolism. 



Anabolism is a building-up. That process through which 

 the living substance is maintained and regenerated by 

 reconstitution and by the assimilation of elaborated food 

 materials. 



Katabolism is a breaking-down of living substance into 

 non-living material. It is that process of chemical change 

 which produces wastes or excretions. 



