PROTOPLASM 



CHAPTER I 



THE LIVING SUBSTANCE 



Protoplasm is living matter in its simplest form. When it 

 occurs, as it nearly always does, in the form of an organized 

 droplet, it is known as a cell, or protoplast. Cells, when per- 

 manently joined together, constitute tissues, and tissues unite to 

 form organisms. Some cells, such as bacteria and amoebae, are 

 complete organisms in themselves. They are known as uni- 

 cellular organisms. The living substance of which cells are com- 

 posed is protoplasm. A too precise definition of protoplasm is 

 Hkely to lead to confusion. Even the specialist finds himself 

 embarrassed by a limited definition. Briefly put, protoplasm 

 is the basic material of life. The word means "primitive 

 form." 



The French zoologist Dujardin is credited with having dis- 

 covered protoplasm in the year 1835. He called it "sarcode." 

 Undoubtedly, earlier investigators — the inimitable observer and 

 portrait painter Rosel von Rosenhof, who drew Amoeba in 1755; 

 O. F. Mtiller, who described living Amoeba in 1773; and Ehren- 

 berg, pioneer protozoologist — saw the living substance, for that 

 is all there is to an amoeba, but to Dujardin apparently belongs 

 the credit of realizing that the material that he saw is the sub- 

 stance which gives life to a cell. Today, nearly a century later, 

 Dujardin's description of protoplasm is as accurate as any that 

 can be given. He said, "Je propose de nommer ainsi ce que 

 d'autres observateurs ont appele une gelee vivante, cette sub- 

 stance glutineuse, diaphane, insoluble dans I'eau, se contractant 

 en masses globuleuses, s'attachant aux aiguilles de dissection, 

 et se laissant etirer comme du mucus, enfin se trouvant dans tous 

 les animaux inferieurs interposee aux autres elements de 

 structure." 



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