382 IOWA DEPARTMENT OF AGRICULTURE. 



chosen, that he is his own enemy and is only hurting himself. Now 1 

 purpose to show that and I call your attention to the illustration which 

 v.ill be made upon the blackboard. 



Suppose the farmer is in search of dairy cattle. We will suppose he 

 begins with one of those common cows that we have been talking about. 

 We will put the letter "C" here on this side (indicating left hand side) 

 and the letter"S" denoting sire with "H" before it. we will say Holstein 

 sire, here on the other side. The farmer proposes to improve his herd 

 using Holstein sires. The difference in the blood elements between thesp 

 animals we will say is represented by 100 per cent. The progeny of the 

 first cross, according to common thought, would possess 50 per cent of 

 the blood elements of the sire and 50 per cent of the blood elements 

 inherited from the dam. Allow me to ask you this question. — is that 

 true or is it not true? Does the progeny in this case possess 50 per cent 

 of the blood properties inherited from the sire and 50 per cent from the 

 dam? It is true. That is the natural thought, but it is not true; the 

 progeny does not inherit simply 50 per cent of the elements or properties 

 possessed by the sire and 50 per cent of the blood elements or properties 

 possessed by the dam. for the reason that here is a dam with mixed 

 blood elements, here is a pure bred sire, we will say one of the best and 

 most prepotent that can be got. Now then, it is very evident that the 

 pro.geny of the first cross will inherit far more than 50 per cent of the 

 properties of the sire and correspondingly less than 50 per cent of the 

 properties of the dam. We cannot tell just exactly how many will be 

 inherited. It will determine upon the relative strength of the blood of the 

 one instance and relatively weaker in the other instance. We will sup- 

 pose the progeny of the cross inherits 75 per cent from the sire and 25 

 per cent from the dam. You have heard the remark that the progeny of 

 a first cross in that kind bears, a close resemblance to the sire! You see 

 how it is; it is following out a natural law of breeding that it is so. 

 You have also heard the statement that the progeny of the second cross 

 does not show as much relative improvement as the progeny of the first 

 cross. That is so and for this reason; at first there was a difference of 

 100 per cent in the blood elements between the sire and the dam; now 

 then there is a difference of only 25 per cent so it is impossible to make 

 as much change in the second instance as in the first. 



But suppose a Holstein sire is used again. Now then there will be 

 about 15 per cent of the blood elements inherited from the sire leaving 

 only 10 per cent from the dam; the same kind of cross is made the third 

 time and there will be about 7 per cent of the sire and 3 per cent of the 

 dam; the same kind of cross is made again and we will say two are 

 inherited here (from the sire) and one here (from the dam). Now the 

 progeny have inherited how many of the elements that are the pro- 

 perties of the sire. We get it by adding up these figures making 99 leav- 

 ing only one on the other side, and here are only four generations of 

 breeding that have been made. Now if another cross is made the fifth 

 cross, why it almost obviates the blood elements from this side (the dam) 

 altogether, so the animal of the fifth generation is about pure blood 



