PRINCIPLES OF HORSE BREEDING 253 



Frequency of variation. — Among farm animals, varia- 

 tion is universal. No two horses are alike. To those 

 unfamiliar with horses, one animal of a well-matched 

 team may look exactly like the other, yet the trained eye 

 will readily recognize differences, and can describe each 

 animal so that those with equal training may recognize 

 it. These differences involve all characters. Two horses 

 of the same breed may differ widely in conformation and 

 carriage, particularly of the neck and tail, in color, qual- 

 ity, action, and the like. 



Kinds of variation. — There are four kinds of variation 

 ■ — quantitative, qualitative, functional and deviation from 

 the common pattern. Quantitative variation has to do 

 with size, and is one of degree only. This is the simplest 

 form of variation and is very common. Two horses of 

 the same breed, one may be large, the other small; or 

 on the same animal one foot may be larger than the 

 others ; and, in like manner, all characters may vary in 

 size. Qualitative variation has to do with quality only, 

 and is distinct from size. Evidences of this are also 

 abundant, the quality of no two horses being alike, as 

 one may have a coarser, rougher hair and a thicker hide. 



Functional variation has to do with functions only, and 

 is distinct from either size or quality. It has reference 

 to the activity of the various organs and parts of the 

 body, such as muscular activity, glandular secretions, and 

 the like. Evidences of this are common, as some horses 

 walk faster than others, and some trot faster, while still 

 others pull heavier loads. Deviation from the common 

 pattern has reference to the irregular appearance of re- 

 peated parts, such as extra toes, extra teats, and the like. 

 This class of variation is seldom observed among horses, 

 but is common among plants, such as the stooling of 

 corn, wheat and oats, as well as the doubling up of 

 flowers. 



Principal causes of variation. — Since variation plays 

 so important a part in improvement, it is of interest to 



