Full text: Problems in eugenics

68Exhibit L i—4. 
IL 3 
L 3a 
L 3b 
L 4Key to Signs. 
S normal male ; ? normal female. 
i colour-blind male ; f colour-blind female. 
O batch of whom there are no particulars. 
O O twins. </> died in infancy. ob : dead. 
X seen and examined. 
X X reported normal, but not seen. 
Hereditary night-blindness with myopia (short sight) affecting. 
21 males and only 1 female in a large pedigree. The night-blindness 
congenital and stationary. Descent always through mothers them­ 
selves unaffected. Mental defects in several of the night-blind 
stock. Other pedigrees of this male-limited night-blindness are on 
record.Key.i and ? night-blind male and female. 
Otherwise the same as for L r. 
Pedigrees of hereditary congenital Nystagmus (involuntary 
rhythmical movements of the eyes) showing two different modes of 
descent. In Figure I, 3a the nystagmus occurs only in males and descends 
through unaffected females. 
In Fig. L 3b both males and females are liable to the disease, and 
either parent may transmit it, although descent is more often through 
mother than father. 
The movements of the eyes are very often accompanied by 
rhythmical movements of the head in the non-sex-limited type 
(Fig. L 3b), but head movements very seldom occur in the male-limited 
type (Fig. L 3a). 
In both types many of those affected have also optical defects of 
the eyes, especially astigmatism. No mental or nerve complications 
in either kind. 
Key. i and ? male and female with Nystagmus. 
Otherwise as for L 1. 
Pedigree of hereditary Cataract. The cataract in this genealogy 
begins in childhood, and usually progresses so as to require operation 
by the time its subject is grown up; results of operation usually good 
and lasting. Most of the affected members still living; of the four

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