366 
Journal of Agricultural Research 
Vol. VII, No. 8 
as that of the sire. Table III gives the number of mares bred by dams 
in the different age classes. The averages show that the young dams 2 to 4 
years old have given offspring with the heaviest cannon bone. The dif¬ 
ference between these and 
the class that has the lowest 
average is 0.159^0.039. 
The average for the class 
with dams 14 to 16 years 
old is 19.341 ±0.035. This 
average is practically the 
same as the average for the 
mares in the classes 5 to 7 
and 8 to 10 year old class. 
This large average is due to 
the 41 mares with a circum¬ 
ference of 20 cm. Of these, * 
20 are sired by stallions 2 
to 7 years old. Figure 3 
shows the percentages of 
mares bred from dams 10 
years old and younger. In this case also the rise begins in the neigh¬ 
borhood of 19.5 cm., and agrees with figures 1 and 2 in this respect. 
Fig. 4.—The percentages of mares of various-sized cannon bones 
bred from both parents under ir years old. 
Table III .—Correlation between the age of the dams and the size of the cannon bone of the 
offspring 
Age of dam. 
Number of offspring having a cannon bone of a 
given size (cm.). 
Average size of 
cannon bone. 
18 
18.5 
19 
19.5 
20 
20.5 
21 
Total. 
Years . 
2 tO 4. .. 
5 to 7 .. 
8 to 10. . .. 
11 to 13.... 
£4 to 16. 
17 and older. 
Total.1 
*3 
21 
22 
14 
13 
7 
34 
48 
3 2 
37 
16 
16 
80 
*55 
1 77 
103 
57 
34 
87 
70 
56 
33 
36 
60 
87 
66 
3 2 
4 i 
22 
IS 
17 
18 
14 
9 
2 
9 
4 
2 
0 
276 
427 
33 2 
260 
171 
117 
Cm. 
19. 404 ±0. 028 
19 * 344 ±°. o 2 3 
19. 340±o. 025 
19. 245±0. 027 
19. 341 ±0. 035 
19. 27I±0. 037 
90 
1S3 
546 
347 
308 
75 
34 
1.583 
r= —0.062 ±0.017 
In order to get a general view of the relation of the age of both parents 
to the size of the cannon bone of their offspring, the writer has computed 
in Table IV the average size of the cannon bone of the female offspring 
grouped according to whether both, either one, or neither of the parents 
was under 11 years of age. The differences between the averages in 
these groups are not striking, except when both parents are under 11 
years old. 
