A HISTORY OF SCIENCE 



the developed individuals of higher organisms the suc- 

 cessive generations of cells become marvellously di- 

 versified in form and in specific functions; there is a 

 wonderful division of labor, special functions being 

 chiefly relegated to definite groups of cells; but from 

 first to last there is no function developed that is not 

 present, in a primitive way, in every cell, however 

 isolated ; nor does the developed cell, however special- 

 ized, ever forget altogether any one of its primordial 

 functions or capacities. All physiology, then, prop- 

 erly interpreted, becomes merely a study of cellular ac- 

 tivities ; and the development of the cell theory takes 

 its place as the great central generalization in physi- 

 ology of the nineteenth century. Something of the 

 later developments of this theory we shall see in 

 another connection. 



ANIMAL CHEMISTRY 



Just at the time when the microscope was opening 

 up the paths that were to lead to the wonderful cell 

 theory, another novel line of interrogation of the liv- 

 ing organism was being put forward by a different set 

 of observers. Two great schools of physiological 

 chemistry had arisen one under guidance of Liebig 

 and Wohler, in Germany, the other dominated by the 

 great French master Jean Baptiste Dumas. Liebig 

 had at one time contemplated the study of medicine, 

 and Dumas had achieved distinction in connection with 

 Prevost, at Geneva, in the field of pure physiology before 

 he turned his attention especially to chemistry. Both 

 these masters, therefore, and Wohler as well, found ab- 

 sorbing interest in those phases of chemistry that have 



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