48 THE TREND OF THE RACE 
proportion of people fail to reach the age at which their hereditary 
taint might become manifest, and since also it is necessary to 
know the whole life history of the individuals concerned. 
Another difficulty is created by the fact that insanity may be 
produced by disease, trauma, alcohol, and various other causes. 
As Dr. Mott says, ‘‘ Acquired syphilis, and in rare cases congeni- 
tal syphilis, are now acknowledged to be the cause of the most 
terrible form of insanity: general paralysis. This disease is fatal 
a few years after the onset of symptoms; heredity plays relatively 
an unimportant part in its causation; it affects all classes in pro- 
portion to their liability to syphilitic infection.” 
The same authority states that ‘‘the cause of 20 per cent of 
the deaths in the London County Asylum is due to general paraly- 
sis,” and that ““we might add another 5 to 10 per cent of cases of 
brain disease dying in asylums with softening of the brain due 
directly or indirectly to syphilis.” Guyer in speaking of general 
paresis states that ‘‘About twenty-two and five-tenths per cent 
of the first admissions to hospitals for the insane from city- 
dwelling men, and eight per cent from men living in the country 
in the state of New York are cases of this kind of insanity.” 
Not to mention other diseases and the various other assignable 
reasons why people become insane, it is evident that a very con- 
siderable percentage of the cases of insanity must be set aside 
in studying the réle of heredity in the causation of this malady. 
Still another difficulty confronts the student of heredity in the 
circumstance that a hereditary proclivity to insanity may be 
present, but owing to favorable conditions of life and the absence 
of events that might upset an unstable nervous constitution, 
a person may escape falling a victim to his inherited defect. It 
is probable that a fair proportion of the hereditarily insane might 
have been saved from their unfortunate fate had they been 
properly shielded from adverse influences. According to many 
statistics, alcohol ranks high among the causes of insanity, but in 
most cases alcohol may have afforded the occasion which led to 
the derangement of a naturally unstable constitution. There 
has accumulated a great deal of evidence that the worst victims of 
