50 THE TREND OF THE RACE 
The first serious attempt to study the inheritance of insanity 
in the light of Mendel’s law was made by Cannon and Rosanoff 
who carefully collected data from the families of 11 insane pa- 
tients in the Kings Park State Hospital, New York. The authors 
employed the method of sending out field workers to study the 
families of the patients, and they were thus able to secure much 
more reliable data than that which is usually collected by hospi- 
tals and asylums. It was concluded that insanity behaves as a 
Mendelian recessive character. The expectations of this hypoth- 
esis that matings of insane with insane (RRXRR) would give 
nothing but insane offspring is quite consistent with the results. 
Out of three such matings yielding 16 offspring, 10 were neuro- 
pathic, 5 died in infancy, and data concerning the remaining 
one were wanting. 
The mating of normal persons heterozygous for neuropathic 
defect, with neuropathics is represented, according to the authors, 
“by 19 matings with a total of 129 offspring. Theoretically 
one-half of these should be neuropathic, and one-half normal, 
but capable of transmitting the neuropathic make-up to their 
progeny. The charts show: 45 neuropathic, 14 normal with 
neuropathic offspring, 20 normal without offspring, 27 normal 
with normal offspring, 20 died in childhood, and concerning 3 
data were uncertain.” 
This is not a very close approximation to the Mendelian 
expectation, under the assumption that we are dealing with 
DRXRR matings. Upon what basis is one of the parents con- 
sidered heterozygous for the neuropathic taint? Evidently the 
authors have counted as heterozygous all those apparently nor- 
mal persons who have produced neuropathic offspring when 
mated with a neuropathic person. This procedure affords a 
perfectly clear case of begging the question, for it assumes the 
truth of the conclusions to be established, and entirely overlooks 
the possibility previously pointed out, that the dominance of the 
normal condition may be variable or imperfect. On the assump- 
tion of Mendelian inheritance the only reliable index of the 
heterozygous make-up of the normal parent is that one of the 
