A HISTORY OF SCIENCE 



tion of the cell contents had been observed as long ago 

 as 1774 by Bonaventura Corti, and rediscovered in 1807 

 by Treviranus, and that these observers had described 

 the phenomenon under the "most unsuitable name of 

 ' rotation of the cell sap.' " Von Mohl recognized that 

 the streaming substance was something quite different 

 from sap. He asserted that the nucleus of the cell lies 

 within this substance and not attached to the cell wall 

 as Schleiden had contended. He saw, too, that the 

 chlorophyl granules, and all other of the cell contents, 

 are incorporated with the "opaque, viscid fluid," and 

 in 1846 he had become so impressed with the impor- 

 tance of this universal cell substance that he gave it 

 the name of protoplasm. Yet in so doing he had no 

 intention of subordinating the cell wall. The fact that 

 Payen, in 1844, had demonstrated that the cell walls of 

 all vegetables, high or low, are composed largely of one 

 substance, cellulose, tended to strengthen the position 

 of the cell wall as the really essential structure, of 

 which the protoplasmic contents were only subsidiary 

 products. 



Meantime, however, the students of animal histology 

 were more and more impressed with the seeming pre- 

 ponderance of cell contents over cell walls in the tissues 

 they studied. They, too, found the cell to be filled with 

 a viscid, slimy fluid capable of motion. To this Du- 

 jardin gave the name of sarcode. Presently it came to 

 be known, through the labors of Kolliker, Nageli, Bisch- 

 off, and various others, that there are numerous lower 

 forms of animal life which seem to be composed of this 

 sarcode, without any cell wall whatever. The same 

 thing seemed to be true of certain cells of higher organ- 



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