CHAPTER XXIX 
MENDELISM IN DOMESTIC ANIMALS 
Although there is a lamentable dearth of specific cases of Mendelian 
inheritance in domestic animals, there is evidence enough to indicate that 
Mendelian principles are of general validity. The difficulty is merely 
a practical one consequent upon the long time and great financial ex- 
penditure which are necessary for collecting critical data in animals. 
Thus far we may state confidently, however, that none of the known facts 
of heredity in farm animals, or in man himself for that matter, is in 
conflict with Mendelian interpretation. Such an interpretation cannot, 
however, be applied satisfactorily until more detailed knowledge has been 
collected of the relation of various characters to one another. Thus far 
practically all Mendelian data in farm animals are from herdbook 
records, and we have gone about as far as it is possible to go with such 
material. Henceforth it will be necessary to depend almost entirely 
upon experimental breeding, if any progress is to be made. This chapter 
is designed to give a record of about the present status of our knowledge 
of Mendelian heredity in farm animals. 
Mendelism in Horses.—Practically all the Mendelian data for the 
horse thus far collected deal with coat color. About the only additional 
data we have is that for the trotting character as opposed to pacing in the 
Standard bred. However, in addition to the characters just mentioned, 
Hurst lists the following contrasted characters as allelomorphic: concave 
and convex faces; straight and curved thighs and hocks; prick-ear, 
drooping ear, forward droop and outward droop of ears; sprinters and 
stayers; liability to cataract blindness, breaking blood-vessels and para- 
lytic roaring (contrasted with normal conditions); long-back and short- 
back. The natural trotting gait appears to be a simple dominant to 
pacing, although there is still considerable doubt as to these characters. 
The records in Table LXIV are of interest in this connection for they 
show that of these ten stallions only one, Electioneer 125, was 
homozygous for the trotting character. It is true that two pacers 
are credited to him, but this may possibly be accounted for by training, 
for it is often possible to change the gait of a horse by proper attention. 
Of coat colors, chestnut appears to be the simplest one. Chestnut 
includes a series of colors varying in depth from dark liver to light sorrel. 
Chestnut mated to chestnut produces only chestnut. Of 14,131 matings 
35 465 
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