138 CARNEGIE INSTITUTION OF WASHINGTON. 



HEREDITY IN MAN. 



The Director has been primarily engaged in analyzing data afforded 

 by the Eugenics Record Office. The following studies have been com- 

 pleted or are, at the present writing, about to be published. 



(1) Violent temper. — An analysis of 66 family histories shows that the 

 tendency to this reaction reappears in successive generations, rarely skip- 

 ping a generation. In one history it is traced through 5 generations; 

 in a large proportion of the histories it is traced through 3 consecutive 

 generations. The few cases in which neither parent of an affected 

 individual is reported to have the tendency to outbursts are explained 

 by obvious insufficiency of the record. The fact that the tendency to 

 outbursts of temper does not skip a generation indicates that it is a 

 positive or dominant trait. That segregation of this tendency occurs 

 is shown by the ratio of affected offspring in any fraternity to the total 

 number of offspring whose emotional history is fully described. From 

 the mating of an uncontrolled and a normal person expectation is that 

 50 per cent of the children will be uncontrolled. A summation of all 

 such children gives a total of 106 affected among 219 sufficiently 

 described, or close to the 50 per cent expected on the hypothesis that 

 the tendency to outbursts of temper is a simple, positive trait. 



(2) Temperament. — -A later study involved a consideration of tem- 

 perament in general, a subject which Galton discussed, inadequately, 

 thirty years ago. It is generally recognized that temperament is 

 hereditary, but there is great diversity of temperaments: some persons 

 are prevailingly gay, others prevailingly somber, and still others pass 

 through alternating cycles of elation and depression. The following 

 hypothesis was tested and met the conditions very satisfactorily: 



"There is in the germ-plasm a factor E which induces the more or less peri- 

 odic occurrence of an excited condition (or an exceptionally strong reactibility 

 to exciting presentations) and its absence, e, which results in a calmness. 

 There is also the factor C which makes for normal cheerfulness of mood, and 

 its absence, c, which permits a more or less periodic depression. Moreover, 

 the factors behave as though in different chromosomes, so that they are 

 inherited independently of each other and may occur in any combination." 



For the test of the hypothesis 89 carefully described family histories 

 were available, and these afforded 147 matings in which the mated 

 pair, their parents (usually), and certain of their offspring were suffi- 

 ciently described for the purposes of the test. The test of the hypothesis 

 is found in a comparison of the expected and actual distribution of 

 temperaments in the children of each sort of mating. Of the 45 pos- 

 sible kinds of matings, 29 were realized. The relations of the sums of 

 the observed to the sums of the expected distributions among the nine 

 classes of temperaments is shown in the following table : 



Observed Expected 



Choleric-cheerful 36 41[j 



Choleric-phlegmatic 25 46 J 



Choleric-melanchoUc 30 19f 



Nervous-cheerful 128 985 



Nervous-phlegmatic 149 1.54g 



Observed Expected 



Nervous-melancholic 63 72^ 



Cahn-cheerful. 77 51| 



Calm-phlegmatic 79 97| 



Calm-melancholic 46 491 



