CHAPTER XI 



HEMIHYPERTROPHY— A TYPE OF MINIMAL 

 TWINNING IN MAN 



Hemihypertrophy is a relatively rare anomaly ob- 

 served in human beings, which has been defined as 

 ''an overgrowth of one half or one side of the body or of 

 a part." 



Quite recently Dr. Arnold Gesell has presented an 

 interesting and illuminating discussion of the etiology of 

 this condition which seems to lead to the conclusion 

 that it is, in all probability, one expression of the wide- 

 spread phenomenon of bilateral twinning. 



There is always a certain amount of asymmetry 

 between the right- and left-hand sides of individuals or 

 between the paired bilateral structures. No human 

 being is exactly the same on the two sides, but usually 

 the discrepancy in the two sides is not sufficient to excite 

 comment. Occasionally, however, individuals have come 

 to the attention of physicians and psychiatrists in which 

 the asymmetry is very striking. In the paper of Dr. 

 Gesell (192 1 ) mentioned above a detailed account is 

 given of a youth, twenty years of age, who was very 

 strikingly larger in all the organs of the right side, head, 

 face, arms, legs, trunk. Even such^median structures as 

 the nose and the penis were distinctly larger on the right 

 side than on the left. Mentally this boy ''must be 

 classified as an imbecile." "The facts clearly indicate," 

 says the author, " that hemihypertrophy should be added 



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