34:0 PRINCIPLES OF STOCK-BREEDING. 



of impure blood several generations back, may appear 

 to be of but little consequence from the very small 

 fraction that apparently represents the proportion of 

 impure blood in the system. 



The facts of atavism, and the observed influence 

 of a cross for many generations afterward, will, how- 

 ever, show that the intensity of an inherited peculi- 

 arity cannot be expressed or represented in mathe- 

 matical terms. 



Fleischmann states 1 that the common sheep in 

 Germany grow from " 5,000 to 5,500 wool-hairs " to 

 the square inch ; while the pure-bred merino sheep 

 that are used in improving them by crossing have 

 from "40,000 to 48,000 wool-hairs" to the square 

 inch. The cross-bred sheep, when a pure merino ram 

 has invariably been- used on one side of the ancestral 

 line, have but " 27,000 wool-hairs " to the square inch 

 " in the twentieth generation," which is about a mean 

 of the numbers observed in the common sheep and 

 the merinos. 



If the " blood " of the original varieties had been 

 transmitted in mathematical proportions, a grade or 

 cross-bred of the twentieth generation would have less 

 than one-millionth part of the " blood " of the com- 

 mon sheep. The number of wool-hairs to the square 

 inch, and other peculiarities of the wool in such cross- 

 bred animals, show that this apparently insignificant 

 fraction of blood has a marked influence on the char- 

 acter of the fleece. 



The completeness of the ancestral record, and the 

 unquestionable purity of blood of every animal in- 



1 " Patent-Office Report," 1847, pp. 269-271. 



