No. 610] SHORTER ARTICLES AND DISCUSSION 



639 



4. We may now consider some numerical illustrations. I 

 us take first the bull Saxton, for which the several observed : 

 breeding coefficients have already been given. We have 



Z - '"^'^ =17 

 800.1953 



Or we may say that Saxton is inbred i 

 tions, taken together 17.8 p 

 sible in those generations. 



For comparison some other figures may be examined. Pearl 

 and Patterson^ have given mean values of the inbreeding co- 

 efficients for four groups of Jersey cattle: (a) Random sample 

 bulls, (&) register of merit bulls, (c) random sample cows, (d) 

 register of merit cows. It will be of interest to reexamine these 

 figures by the method here described. The results are given in 

 Table II. 



TABLE II 



Total Inbreeding Coefficients for Jersey Cattle. (Pearl and Patter- 



1. General population (random sample) bulls 



2. Eegister of merit bulls j 



4. Register of merit cows i 



From this table we see that American Jersey cattle, as judged 

 by random samples of the general population, are about 28 to 30 

 per cent, as closely inbred as the maximum possible amount, 

 taking account of the first eight ancestral generations as a wliole. 



It is not desirable to go further into the discussion of these 

 Jersey data, since the purpose of this note is simply an exposition 

 of method. This new method makes possible exact and unique 

 numerical comparison between pedigrees in respect of the degree 

 of inbreeding which they exhibit in the same number of ancestral 

 generations. 



Raymond Pearl 



5 Pearl, R., and Patterson, S. W., Troc. Nat. Acad. Sci., Vol. 2, p. 60, 

 1916. 



25.39 30.48 27.94 



24.52 i 29.17 j 81.85 



27.46 31.74 29.60 



20.72 I 27.08 j 23.90 



