28 THE TREND OF THE RACE 
is often difficult to estimate; but it requires no great discernment 
to perceive that many rather confident expressions of opinion are 
based on lack of familiarity with the principles of hereditary 
transmission, or a very inadequate acquaintance with the investi- 
gations that have been made in this field. 
The method of investigation employed by the Eugenics Record 
Office at Cold Spring Harbor, Long Island, is one that is in some 
respects considerably superior to those commonly followed. 
Instead of collecting mass statistics a more intensive study is 
made of special cases. For this purpose trained field workers are 
employed who make the acquaintance of the relatives of the 
patients investigated, get into friendly relations with them, and 
through personal impressions and a knowledge of their history are 
enabled to form a tolerably accurate judgment of their mental 
status. The full and careful study of several pedigrees of mental 
defectives promises to throw more light on the precise method in 
which mental defects are inherited than any amount of unana- 
lyzed data collected from the loose records of institutions. Field 
workers need to be psychologists skilled in the methods of meas- 
uring intelligence and of detecting mental aberrations, and en- 
dowed with the attributes of tact, patience and an ingratiating 
personality. Data secured by field workers have already been 
proven of considerable value in throwing light on the probable 
mode of transmission of mental defect, although there is room for 
considerable refinement of method and thoroughness of enquiry 
in much of the investigation which has thus far been carried on. 
The intensive study of pedigrees has been the chief method of 
those whose aim it has been to show that mental defect is trans- 
mitted according to Mendel’s law. Whatever may be the issue of 
the controversy over whether or not mental defects behave as 
mendelizing unit characters, insight into the question can only 
come by the thorough, critical and unbiased study of particular 
pedigrees. 
