PROTOPLASM 



the matter under investigation unless an experi- 

 ment be made. 



We stand before the question as to what may be 

 made responsible for this continuous change of 

 form and of chemical properties. 



Inspection with the naked eye could not have 

 brought any solution of this question. Nor was 

 chemical analysis able to contribute facts of 

 importance. Only to the microscopical investiga- 

 tion of the cells do we owe our knowledge of the 

 organs of life. And here again animal cells have 

 proved to be much less accessible for searching 

 analysis than the cells of plants. It was in 1840 

 that Hugo von Mohl, of Tubingen, drew attention 

 to the important fact that plant cells have the 

 qualifications of life only as long as they contain 

 a slimy layer along the cell wall, which layer was 

 at first called the Primordial Utricle. The thorough 

 examination of anatomical facts led Mohl and 

 Schleiden to the conviction that all the organs 

 of the cell originate in this slimy matter. Con- 

 sequently the mucous layer was called Protoplasm. 



In the following decades it was fully established 

 that the presence of life is extremely closely 

 connected with the presence of active protoplasm. 

 The physiologists Bruecke and Kuehne may be 

 called the originators of the view now universally 

 adopted that Protoplasm is the Living Substance 

 in animals and plants. The general and funda- 

 mental properties of protoplasm in both are the 

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