138 



Cells; or, Evolution. 



it to another. It is the physical unit. And life, it 

 is now found, may be entire in little organisms 

 which consist each of only one cell, and are called 

 4i unicellular." In the great organisms too, consist- 

 ing of many cells, and called "multicellular," it is 

 still the same physical unit of organic matter that 

 the organism extracts from the pabulum, transforms 

 into fitting material by digestion, informs with life, 

 and which, as a new living cell, it adds to its struct- 

 ure in skin, bone, cartilage, muscle, etc. In every 

 case therefore, the cell is conceived to be the last 

 physical unit, wherein life can be found, and in less 

 than which life cunnot be. 



151. Inside the wall or envelope of the cell, and 

 sometimes constituting the whole of it, is found an 

 element which seems indispensable. It 

 is a liquid substance of slimy consist- 

 ency; and, to follow the description of Gordon 

 Salamon in his recent lectures on Yeast, delivered 

 before the Society of Arts, it is "endowed with 

 specific organization, and is capable of exhibiting 

 motion." This substance has been called proto- 

 plasm. Sometimes, as in the early stages of the 

 life-history of certain organisms like the slime 

 fungi, the protoplasm is not contained in any cell 

 envelope whatever; yet it can express its vitality in 

 terms of motion and constructive increase, that is, 

 it can move, grow, and multiply. Life is unknown 

 without the presence of this protoplasm, w T hich is 

 to be found in every organic living cell, whether 



Protoplasm. 



