The Oryamsm and Its Cells 171 



it is necessary to investigate the properties of the constit- 

 uent parts of organisms before we can hope to under- 

 stand them in their entirety. Because of our limited knowl- 

 edge , we are for the present setting ourselves an impossible 

 task if we expect to determine with certainty by means of 

 a few experiments exactly the combination of factors in- 

 volved in the normal ontogeny of any particular structure. 

 In fact we can never 'explain' the processes of normal de- 

 velopment with more than a certain degree of probability, 

 until we succeed in synthesizing organisms from simple 

 known constituents or construct working models that show 

 all of the essential activities of organisms achievements 

 from which we still are very far removed. Syntheses may 

 possibly be made, however, at different stages of the analysis 

 with components of greater or less complexity. Thus it may 

 he possible to extend the remarkable experiments of H. V. 

 Wilson." 2<J 



The manifest worth and practicability of the manipula- 

 tive methods introduced by Harrison assured their quick 

 adoption by other workers, and already a considerable litera- 

 ture has come into being dealing with "surviving tissues." 

 Owing, it seems, largely to the fact that Dr. Carrel has vig- 

 orously and skillfully applied the methods in the interest of 

 surgery, he has attained wider distinction in connection with 

 the researches than has any one else, though several other 

 biologists and physicians have increased knowledge substan- 

 tially by the new instrument of discovery. 



The remarkable viability of tissues removed from their 

 native setting in the organism and kept under artificial con- 

 ditions is well brought out in a recent paper by A. H. 

 Klnling. This investigator made cultures of fragments of 

 the heart of chick embryos seven to eighteen days old, a 

 few of which lived and flourished nearly a year. "The ex- 

 periments show," said Kbi-ling, "that connective tissue can 

 l>r kept in a condition of active growth outside of the organ- 



