In case the particular trait has been clearly analyzed on the Mendelian or other basis, the application of the definite rule of inheritance to the particular case is given. But, as a matter of fact, most human qualities - physical, mental and temperametal - which are known to be hereditary, i.e., to run-in-families, are not based definitely upon one sumple[sic] or even upon a few Mendelian genes, but rather upon a complex of such genes, the analysis of which on the Mendelian basis is, as yet, exceedingly unsatisfactory. Thus the type of information which in most cases is given to the inquirer is based upon the actuarial analysis of parallel family trees which have the same trait running through their branches. The main advantage of being associated with the archives of the Eugenics Record Office is that not only many parallel first-hand pedigrees are, in cases of most inquiries, available for analysis, but also the world's stock of knowledge of rules of inheritance of a given trait are in hand and available for critical application to the specific problem by the clinic. The Eugenics Record Office has built up the most complete stock of first-hand human pedigrees of this sort to be found anywhere. [end]