THE STORY OF NINETEENTH-CENTURY SCIENCE 



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

 choff, 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- 

 isms, as the blood corpuscles. Particularly in the case 

 of cells that change their shape markedly, moving about 

 in consequence of the streaming of their sarcode, did it 

 seem certain that no cell wall is present ; or that, if pres- 

 ent, its role must be insignificant. 



And so histologists came to question whether, after 

 all, the cell contents rather than the enclosing wall must 

 not be the really essential structure, and the weight of 

 increasing observations finally left no escape from the 

 conclusion that such is really the case. But attention 

 being thus focalized on the cell contents, it was at once 

 apparent that there is a far closer similarity between 

 the ultimate particles of vegetables and those of ani- 

 mals than had been supposed. Cellulose and animal 

 membrane being now regarded as mere by-products, the 

 way was clear for the recognition of the fact that veg- 

 etable protoplasm and animal sarcode are marvellously 

 similar in appearance and general properties. The closer 

 the observation the more striking seemed this similar- 

 ity ; and finally, about 1860, it was demonstrated by 

 Heinrich de Bary and by Max Schultze that the two are 

 to all intents and purposes identical. Even earlier Ke- 

 mak had reached a similar conclusion, and applied von 

 Mohl's word protoplasm to animal cell contents, and 

 now this application soon became universal. Thence- 

 forth this protoplasm was to assume the utmost impor- 

 tance in the physiological world, being recognized as the 

 universal " physical basis of life," vegetable and animal 



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