CROSSING AND IN-AND-IN BREEDING 15 



second or later generation. Fof this reason many breeders 

 at one time objected to mingling the blood of Booth and 

 of Bates Shorthorns, but the benefits resulting from the com- 

 mingling of Booth, Bates, and Cruickshank strains of blood, 

 when skilfully carried out, have been found to outweigh the 

 disadvantages. 



Close in-and-in breeding, "incestuous breeding," or 

 the pairing of animals very closely related to each other, 

 ultimately causes great loss of constitutional vigour, loss of 

 size and fertility, and sometimes malformation as in the case 

 of a pig bred at Twiglees, Lockerbie, which at birth lacked 

 a number of the vertebral segments. Pigs show the bad 

 effects of consanguinity sooner than any other farm animals. 

 This is perhaps on account of their comparatively solitary 

 habits when in a state of nature. Gregarious animals do not 

 suffer so much ; they have been more accustomed to it, and 

 Nature has accommodated herself to the circumstances. 



Darwin says, in no hesitating manner : " The gain of 

 constitutional vigour derived from an occasional cross between 

 individuals of the same variety, but belonging to distant 

 families, has not been so largely or so frequently discussed 

 as have the evil effects of too close interbreeding; but the 

 former point is the more important of the two, inasmuch as 

 the evidence is more decisive. The evil results from close 

 interbreeding are difficult to detect, for they accumulate 

 slowly and differ much in degree with different species ; while 

 the good effects which almost invariably follow a cross are 

 from the first manifest." 



He summarises, in conclusion, as follows : "The crossing 

 of animals and plants which are not closely related to each 

 other is highly beneficial, or even necessary, and interbreeding 

 prolonged during many generations is highly injurious." 



Shorthorn cattle have proved to be not so much the 

 worse for in-and-in breeding as most other stock, although 

 injury has been done, as will be mentioned subsequently. 

 The distinct type peculiar to them has undoubtedly been 

 formed and fixed by in-and-in breeding. The most prominent 

 advantage of in-breeding is this stamping of family characters 

 or types, and it cannot well be dispensed with in the forma- 

 tion of new breeds or the improvement of old ones. But it is 

 neither a weapon to be handled with safety by the novice or 

 amateur, nor of service to the practical breeder who produces 



