THE MEASUREMENT OF THE INTENSITY OF INBREEDING. I33 



Table 3. 



Working Table Used in Calculating the Coefficients of 



inbreeding for Pedigree Table II. 



Animal. 



Sisera's Stoke Pogis. 

 Patrick Fawkes .... 



Balm 



Totals... 



Ancestral Generation. 



3. 4. 



2 4 



1 

 1 



2 6 



in (i). These totals, multiplied by 100, have then merely to be 

 divided by p^+i in order to obtain the successive Z's. The 

 whole operation may be very quickly carried out. It is not 

 necessary, in fact, to fill out the whole of the later columns of 

 the table, the entries may be cumulated. 

 For the present pedigree we have 



Zo = o, as always* 

 100 (i) 



Z:=.— — = 25% 



z^.= 



Zo 



4 

 100 (2) 



= 25% 



100 (6) 

 16 



=^ 37-5% 



From these values it is seen that in the first four ancestral 

 generations the cow Bess Weaver is 37.5 percent inbred. This 

 is a perfectly definite figure, directly comparable with similar 

 constants for other animals. Of course, if we were to go back 

 more generations we should find Bess Weaver still more inbred, 

 that is, the coefficients would grow larger with each case of 

 the mating of relatives. Since the case is cited here merely for 

 illustration of method, four generations only are considered. 



* The apparent paradox implied in the fact that Zo must always be 

 zero, or in other words that in the first ancestral generation, considered 

 alone, there is no inbreeding will be cleared up, if it strikes the reader 

 as paradoxical, by a reconsideration of the general principle numbered 

 5 on p. 127. The point of course is that it is impossible to say whether 

 the parents are or are not related to one another until something is 

 known of their parentage, or in other words, until a second ancestral 

 generation is considered. 



