GENETICS: C. B. DAVENPORT 
283 
system here presented has the support of much better evidence than 
that for atomic evolution from the standpoint of astronomy alone. 
We wish to thank Professor A. C. Lunn of the Department of 
Mathematics, for outlining for us the method for determining the dis- 
tances between the positive and negative electrons. 
1 Moseley, Phil Mag., London, 26, 1024; 27, 703. 
2 Lorentz, The Theory of Electrons, p. 47. 
3 K. Fajans, Physik. Zs., Leipzig, 14, 131 and 136. 
*F. Soddy, Chem. News, London, 107, 97; Jahrb. RadioakL, 10, 188. 
5 Russell, Chem. News, London, 107, 49. 
* Von Hevesy, Physik. Zs., Leipzig, 14, 49. 
7 Fleck, Trans. Chem. Sec, 103, 381 and 1052. 
^Rydberg, Zs. anorg. Chem., Hamburg, 14, 86-7. 
9 Richards and Willard, /. Amer. Chem. Soc., 32, 4 (1910). 
W. A. Noyes, Textbook of Chemistry, p, 72. 
^1 Hale, The Study of Stellar Evolution. 
HUNTINGTON'S CHOREA IN RELATION TO HEREDITY 
AND EUGENICS 
By C. B. Davenport 
STATION FOR EXPERIMENTAL EVOLUTION. CARNEGIE INSTITUTION OF WASHINGTON 
Read before the Academy. April 20, 1915. Received. April 5, 1915 
It is now generally conceded that predisposition plays an important 
role in mental disorder but the views as to the nature of its part are 
very diverse and hazy. Some investigators conclude that there is an 
inheritance of a particular type of mental trouble, while others conceive 
that only a general psychopathic constitution is inherited. Again a 
difference of view maintains as to the nature of the recognized mental 
^diseases' — by some these are regarded as distinct 'entities,' manifesta- 
tions of a single, indivisible, disturbing factor. Others conceive of them 
as syndromes or chance associations of symptoms. Even those who 
hold the latter view would perhaps except as the one clear case of a 
neuropathic entity the condition known as 'Huntington's Chorea.' This 
chorea is defined by the following traits: (1) persistent tremors of the 
head, appendages and trunk; (2) the onset of such tremors in middle 
or late life; (3) the progressive nature of the tremors; and (4) progressive 
mental deterioration. These characters are frequently found together; 
is their association a necessary one? 
A study of four family complexes in eastern Long Island, south-west- 
ern Connecticut, south-central Connecticut and eastern Massachusetts 
which show nearly a thousand cases of Huntington's chorea yields the 
