542 IOWA DEPARTMENT OF AGMCULTTJRE. 



may be divided into several heads, viz., defective formation, defective 

 quality and insufficient quantity of tissue and temperament. Within cer- 

 tain limits the practised eye of the observant horseman can determine 

 in sire or dam the existence of these defects that are transmissable to the 

 offspring and predispose it to the d^elopment of unsoundness. It is 

 claimed by some authorities that some horses and mares possess a pecu- 

 liar habit of body, an indefinable something about them which predisposes 

 them to the development of some unsoundness and also their progeny. 

 Such cases are rare, however, and their supposed existence is very fre- 

 quently the result of the inability of an observer to appreciate the exist- 

 ense of detectible predisposing causes. U this indefinable something is 

 the determining cause of predisposition in some cases, then the only posi- 

 tive evidence of its existence is the devel®ped unsoundngss. 



This theory presupposes that none of the detectible predisposing causes 

 already mentioned exists in sufficient degree ki such cases so that when 

 subjects of them are subjected to more than ordinary exciting ones, they 

 would develope unsoundness, unless the peculiar habit of body exists. It 

 also is an acknowledgement of the helplessness of breeders in a consider- 

 able degree to prevent breeding coKs with an inherent tendency to 

 unsoundness. No matter how capable and careful a breeder is he will 

 produce a certain percentage of unsound stock, due to heredity, but with 

 care It can be reduced to a small one. Many breeders use a sire from con- 

 venience or from some quality that he possesses, such as speed, action, 

 style or disposition, knowing that they are taking a chance of perpetuat- 

 ing some tendency to unsoundness that he possesses. Favorite mares are 

 also bred with a disregard to the well established principle that like 

 begets like even when they are the victims of hereditary unsoundness or a 

 strong predisposition to it. The successful breeder must divest himself 

 of all sentiment and be capable of appreciating all defects which consti- 

 tute predisposition to unsoundness. Of the prgdisposing causes defective 

 formation is a most fertile one. 



The predisposition to navicular disease is hereditary. Horses with 

 narrow deep heels and shoBt hoofs are predisposed to it. Some obser- 

 ver may say: "But look at the large number of horses one sees with 

 narrow deep heels and short hoofs that have not got navicular disease." 

 Of course such an argument is fallacious, as there may be many com- 

 pensating conditions that will tend to neutralize the tendency to this 

 disease in some subjects. A horse with the formation of foot described, 

 ev^n although he is subjected to the exciting causes of hard, fast and 

 steady work and irrational and infrequent shoeing, may be endowed by 

 nature with a very light step. Nothing tends to prevent wear and tear 

 of the legs and feet like light stepping. Here then is an example of an 

 influence which tends to counterbalance the ill effects of a defective 

 formation, but renders complicated the study of formation in predispos- 

 ing to unsoundness. One then has to weigh the influence of compensat- 

 ing conditions in determining the ill consequences likely to result from 

 defective formations of foot, when transmitted to offspring. That defec- 

 tive formations of feet are handed down to progeny there is no manner 

 of doubt. 



