20 BULLETIN 1121, U. S. DEPARTMENT OF AGRICULTURE. 
THE PERCENTAGE RAISED OF ALL YOUNG BORN. 
The percentage raised of all young born is simply the product of 
the two which we have been considering. Figure 10 brings out the 
superiority of crossbred young from inbred dams (CO, CA) over 
inbreds, and the still greater superiority of crossbred young from 
crossbred dams (AC, CC). The record of the first generation inbreds 
from crossbred dams (C1) is a little higher than theory would indicate. 
There is, however, a decline in the next generation of renewed inbreed- 
ing (C2) of almost the expected amount. It is noteworthy that the 
record of the random-bred stock (B) is practically reached by cross- 
breeding involving only three or four of the inbred families. 
One of the most striking results is the great advance of the cross- 
breds over the best of the inbred families. The superiority of the 
best inbred family over the average is increased more than fourfold. 
Wet 
* 
Tae Nee cae 
eA 
Eg ET eae a ESE 
30 
Fic. 10.—The percentage raised to 83 days of all young born, 1916-1919. Indices correcting for effects of 
size of litter and seasonal conditions. (See Fig. 8 for explanation of symbols.) 
This is a much greater relative increase than shown in the case of 
either component percentage. The reason is easily discovered. An 
inbred family which is above the average in percentage born alive 
is perhaps more likely than not to be below the average in the per- 
centage of these raised. It thus comes about that there is no more 
differentiation among the families in the total percentage raised than 
in either component. The second generation crossbreds, on the 
other hand, are superior in both components and thus very much 
superior in the product. We have here a good illustration of the 
way in which a great superiority of a crossbred stock over the best of 
its ancestral inbred families with respect to a complex character 
may be built up out of mere dominance of vigor over weakness in a 
number of more elementary characters which are distributed at 
random among the inbred families. Further illustration of this 
point will be taken up later. 
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