FIFTH LECTURE. 



ON THE NATURE OE CELL-ORGANIZATION. 1 



S. WAT ASK. 

 I. 



IF the true nature of a higher organism cannot be 

 understood without considering the structure and the function 

 of its component organs, it is equally certain that the nature 

 of an individual cell cannot be made intelligible without a 

 comprehensive study of the different organs of which it is 

 composed. 



At the present time, when morphologists are explaining 

 the origin and development of the different structures in an 

 organism in terms of cell-growth and of cell-metamorphosis, 

 and when physiologists are referring the activities of the whole 

 organism back to the functions of its component cells, it is 

 natural that considerable attention should now be directed 

 toward the solution of more elementary problems concerning 

 the nature of the cell-organism. The cell-theory, while it 

 explains the structure and functions of a tissue on a cellular 

 basis, leaves the real nature of the cell itself unexplained. 



The vital properties of a nucleated cell manifest themselves 

 in various ways, but they may be broadly classified under two 

 categories, viz., (i), those tending to the preservation of the 

 individual cell, and (2), those tending to the maintenance of 

 the species. Under the first are included the general phe- 

 nomena of cell-metabolism and different forms of irritability, 

 and under the second those of cell-division and cell-fusion. 



Diverse as are these special cell-phenomena which tend 

 directly or indirectly to the preservation of the cell, it must 



1 Lecture given before the Biological Club of the University of Chicago, 

 February 7, 1893, anc ^ afterward written out in the present form. 



