Nov. 20, 1916 
Size of Cannon Bone 
363 
are calculated from the original figures before they were grouped in a 
correlation table. The age of the stallions is arranged in classes with 
3-year intervals in each class—that is, class 1 is composed of stallions 
2 to 4 years old; class 2 is 
composed of stallions 5 to 7 
years old, etc. In this no¬ 
tation 2 to 4 means under 5, 
5 to 7 means under 8, and 
so on. The correlation co¬ 
efficient is —0.061 ±0.012. 
Although the coefficient of 
correlation is five times as 
large as the probable error, 
the negative correlation is 
so small that it indicates only 
a very slight tendency for 
older sires to beget daughters with smaller cannon bones. The average 
size of cannon bone decreases slightly as the age of the sires increases. 
The difference between size of cannon bone for the mares whose sires 
are 5 to 7 years old and the mares whose sires are 17 years of age or 
older is 0.111 ±0.036. 
A9.S 20 2G*S 2/CM. 
Fig. i.—C urve showing the percentages of mares with 
various-sized cannon bones, sired by stallions under n 
years old. 
Table) I .—Correlation between the age of the sires and the measurement of the cannon 
bones of the female offspring 
Age of stallion. 
Number of female offspring having a camion bone of a given 
size (cm.). 
Average size of 
18 
18. s 
19 
19 -S 
20 
20.5 
21 
Total. 
cannon bone. 
, Years. 
2 tO 4 . 
26 
. 58 
143 
96 
72 
14 
6 
415 
Cm. 
19. 273±0. 021 
5 to 7 . 
73 
*37 
387 
182 
178 
44 
22 
h 023 
691 
19. 272±0. 014 
8 to 10. 
60 
99 
252 
107 
135 
22 
16 
19. 244±0. OI7 
11 to 13. 
33 
61 
166 
75 
73 
11 
7 
426 
10. 2I9±0. 021 
14 to 16. 
24 
37 
102 
47 
37 
7 
2 
256 
19. i75±o. 026 
17 and older. 
10 
23 
58 
26 
20 
3 
0 
140 
19. i6i±o, 033 
Total. 
226 
4 i$ 
1,108 
533 
5*5 
101 
53 
2 > 95 1 
r= —0.061 ±0.012 
Figure 1 shows the percentages of all mares of various size classes sired 
by stallions 10 years and younger. To be sure, more mares of all classes 
were sired by stallions under 11 years old, but it is interesting to note 
that gradually increasing percentages of the larger mares were sired by 
these younger stallions. To state this differently, mares whose cannon 
bone measures more than 19.5 cm. are more likely to come from sires 
under 11 years of age than are the mares whose cannon bone measures 
under 19.5 cm. There is a perceptible rise in the curve beginning at the 
19.5 cm. Figure 1 was plotted from Table I by taking the ratio of the 
