408 



BIOLOGY: GENERAL AND MEDICAL 



The question may be asked why the tumor tissue 

 behaves differently from the normal tissue when trans- 

 planted, for we remember that even in the homologous 

 and autoplastic transplantations of normal tissues the 

 grafts are usually subject to decadence, death, and ab- 

 sorption. The answer seems to be found in the abnor- 

 mal impulse of growth that characterized the tumor 

 tissue and stamps it as such. It is tissue that would 



E 



FIG. 145. Different modes of grafting: I, crown grafting; II, splice grafting; 

 III, bud grafting; W, stock; E, scion. (Strasburger, Noll, Schenck, and Karsten.) 



grow unrestrictedly in its normal environment, and 

 continues to do so when transplanted. 



When we come to consider the conditions of successful 

 grafting in the vegetable world we find that with certain 

 exceptions they form a parallel with what has already 

 been found in the animal world. That is, their success 

 or failure depends chiefly upon the blood relationship 

 of the plants concerned, though this restriction is not 

 so closely defined as among animals. Plants of the 

 same species can, other things being equal, easily be 



