ae, CIRCULAR 824, U. S. DEPT. OF AGRICULTURE 
DISCUSSION 
The results presented must be considered as only an approach to 
many of the problems involved. Although the number of animals 
was fairly large considering the relatively long ‘interval between 
generations of horses and the expense of raising and training them, 
the number and distribution of progeny by sires or dams were not 
adequate to more than indicate some of the possibilities from the 
standpoint of inheritance. Moreover, most of the tests should be 
repeated several times with each horse in order to get reliable esti- 
mates of its ability. Ina preliminary study, Phillips, Brier, and Lam- 
bert (7) found this to be true for time required to walk or trot a mile 
in the carriage. In repeated tests, however, with the same horses 
Tae saddle at the trot no significant differences were noted between 
the tests. 
No check has been made of the reliability of the data obtained for 
the time required to walk a mile under saddle or to cover the 11.35- 
mile course; for the riders’ scores for ease of handling, performance of 
gaits, and ease of gaits to riders; or for the scores given by the trained 
observers. 
The significant differences between the progeny of different sires 
oive strong indications that factors controlling the following charac- 
ters are inherited: Speed at the walk and on the 11.35-mile course, 
height to floor of chest, length from point of shoulder to point of hip, 
style and beauty, slope of croup and shoulder, and action at the trot. 
Such significant differences as were found are undoubtedly due to 
both environmental and genetic factors. With the data available 
there is no way of accurately measuring all these effects. However, 
in the case of speed, which one would expect would be affected mate- 
rially by environmental influences, the indications of the influence of 
inheritance are strengthened by the significant differences for speed 
at the walk and on the 11.35-mile course within the same years and 
with the same riders, the significant differences for speed at the walk 
between the offspring of different dams, and the significant differences 
between the offspring of certain sires mated to the same dams. The 
fact that differences in temperature and humidity at the time of the 
test did not, on the average, have a significant effect also tends to 
eliminate these environmental factors. Some of the differences that 
were not statistically significant, such as differences between the off- 
spring of the different sires for speed at the trot in the same years 
and with the same riders, might with repeated experiments and differ- 
ent samples prove to be inherited to a measurable degree. 
Many of the interrelationships among the characters have not been 
adequately studied. Some of these may be complex, as Dawson (1) 
found in studying the relationship of weight and heart girth to pulling 
ability in draft horses. A number of the associations found may be 
coincidental. For example, some of the sires might transmit both 
small feet and speed to their offspring, thereby making it appear that 
speed was dependent on the size of the feet, when actually there was 
no relationship other than that both characters were inherited to- 
gether and the sample was not large enough to randomize such 
occurrences. 
