608 GENETICS IN RELATION TO AGRICULTURE 
For after all in spite of our present dearth of detailed knowledge of 
heredity in domestic animals there is no real cause for discouragement. 
It is not yet two decades since the rediscovery of Mendel’s law of heredity; 
and the most rapid progress has been made within the last five years. 
It is not, therefore, at all strange that we have not yet obtained extended 
data from experimental research; in fact, most of the Mendelian data 
we now have on the larger domestic animals is of the interpretive kind, 
that is, the conclusions have been drawn from records already in existence. 
Experimental research such as has been employed in the study of the 
inheritance of coat color in rodents, has not yet been carried out to 
determine the relations of the various coat colors and patterns in horses 
and cattle; the best that has been found possible thus far is the study of 
herdbook records and breeders’ notes. 
The Need of Research.—Students know too well how difficult it is 
to make due allowances for all the variable factors which may enter into 
a given body of data. Consequently, however simple the conditions 
may be, those conclusions which are based on records as crude as those of 
herd books and breeders’ notes are subject to a great deal of uncertainty. 
Moreover, it is usually impossible under practical conditions to find 
matings which have been carried out in such a way as to give crucial 
tests of a given hypothesis of factor relations. We have emphasized this 
difficulty in the discussion of Mendelian inheritance in domestic animals, 
pointing out that very.often alternative interpretations could be made of 
the crude data extant; interpretations which could be very easily sub- 
jected to a crucial test in the case of accurate scientific research. In the 
domestic animals, as in Drosophila, the ideal goal of genetic analysis 
should be that which determines accurately the mode of inheritance 
and expression of as many Mendelian factors as is possible. The task 
is difficult, but the increasing knowledge of heredity in lower forms will 
immensely simplify its execution. 
The time and expense necessary for carrying out studies of heredity 
has often deterred investigators from attacking problems in higher 
animals because the possibility of economic application of the results 
has seemed to be remote or almost certainly nil. But this is not the 
point at issue, as may be clearly seen when the interrelations between 
factors are considered. Accurate determination, for example, of the 
various factors and factor interactions in the heredity of coat color in 
cattle would give a secure and definite basis from which to prosecute other 
investigations more intimately concerned with problems of economic im- 
portance. It iseven highly justifiable to commend such investigations, 
because the problem is then first approached in its simplest form. There 
is grave question as to the advisability of plunging pell mell into difficult 
problems before the simpler ones have been solved, were it not for the 
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