CHAPTER XIII. 



Heredity (continued)— A Consideration of the Different Modes by which 

 Organic Potentialities may become Actualities — Some further Bearings 

 of the Principle of Reversion upon. Pathology — Summary. 



Potentiality. — Allusion has been made more than once to 

 that curious property termed potentiality. This property is 

 possessed by living aggregates in common with other aggrega- 

 tions of matter; here, it is only necessary for us to speak of the 

 potentialities of living organisms. A property is said to exist 

 potentially when it is not actually present, but is capable, under 

 certain circumstances, of being called into actual being. 



I am led to consider this subject here, because the partial 

 dissolutions and evolutions of which we have just spoken 

 afford very good examples of the way in which potentialities 

 may become actualities. There are, however, other ways in 

 which this may take place. 



In treating of the causes of potential manifestations, I shall 

 consider the individual and not the race : the reappearance of 

 a long-lost ancestral character in the offspring of crossed 

 parents may be said to pertain rather to the race than the in- 

 dividual, seeing that it is not so much the manifestation of a 

 potentiality by an individual, as of parental potentialities. 



Confining our attention, then, to the individual, we shall 

 find that there are at least four causes of potential manifesta- 

 tions : — 



1 . Partial dissolutions of disease. 



2 . Partial evolutions of disease. 



3. Normal organic evolutions. 



4. Interference with the proper action of ovaries or 



testicles. 

 I. The partial dissolutions of disease affords a particularly 

 good example of the manner in which a potentiality may become 



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