PROBLEMS OF MODERN SCIENCE 



empirical study of a single isolated organism, like 

 the human body, would be almost meaningless to 

 the philosophical biologist as meaningless as the 

 study of a brief period of history without any 

 reference to its antecedents. With the improve- 

 ment of our methods above all with the advent 

 of the microscope and the elaboration of micro- 

 scopical technique our morphological studies are 

 becoming more and more minute and exhaus- 

 tive, and it has become necessary to recognise 

 two subordinate branches dependent entirely upon 

 microscopical investigation. These are Histology, 

 which deals with the tissues of which the organs of 

 the body are built up, and Cytology, which deals 

 with the cells of which the tissues in their turn are 

 composed. It is in the domain of Cytology that 

 much of the most important progress in biological 

 science has lately taken place. The cell is the unit 

 of organic structure, and the study of cells even 

 if undertaken exclusively from the morphological 

 standpoint furnishes more than enough occupa- 

 tion for the lifetime of a highly-trained specialist. 

 Each one of the many thousand different kinds of 

 cells already known to us has a minute structure 

 complex beyond our powers of analysis, and it is 

 upon this structure that that of the entire organism 

 depends. 



The study of the microscopical structure of 

 the germ-cells has given us our first real insight 

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