906 
Journal of Agricultural Research 
Vol. XXX, No. 10 
MISCELLANEOUS FACTORS 
The number of copulations as related 
to the sex of the offspring showed no 
effect, but the females were in excess in 
all classes except the four-copulation 
and five-copulation classes, in each of 
which the total number involved is less 
than 15. A large effect could scarcely 
be expected (16) because the number 
of copulations was in no case greater 
than five, and where there was more 
than one the liquid from the preceding 
copulations was mixed all together with 
that of the last, and therefore it is im¬ 
possible to know whether a given one 
of the young was produced by a sperma¬ 
tozoon from the first or a later copula¬ 
tion. 
It is hardly to be expected that the 
amounts of liquid recovered by the 
methods used in this experiment would 
be comparable enough to the amounts 
actually ejaculated to show a difference 
in the sex ratios produced by different 
amounts, even if such a difference 
existed. The sexes were either exactly 
even or there was a slight excess of 
females, which approached significance 
in only one case and did not seem to 
vary uniformly as related to the amount 
of liquid. 
The microscopically distinguishable 
differences in the activity of the sper¬ 
matozoa did not show any correspond¬ 
ing differences in the sex ratios of the 
offspring produced. This is not sur¬ 
prising, since no liquid was used for 
insemination unless there was at least 
a moderate number of fairly active 
spermatozoa to be seen in it. 
RELATION OF TYPE OF BREEDING TO 
SUCCESS IN INDUCING PREGNANCY 
The records kept before the centri¬ 
fuging was begun were not detailed 
enough to permit taking any figures as 
to services which were natural in every 
way. Table VIII gives the number 
and percentage of services and insemi¬ 
nations which resulted in pregnancy 
and also the number which did not 
result in pregnancy. The percentage 
of success is figured only for those 
methods which were tried at least 30 
times. 
Several factors combine to make the 
data in Table VIII only approximate. 
A number of females would accept ser¬ 
vice while pregnant and a number were 
barren either through an infection in 
the Fallopian tubes or for some other 
reason. Such females were kept when 
there was room for them and were used 
for the recovery of seminal fluid, be- 
ca use the main object of the experi¬ 
ment was the production of the largest 
possible number of young by insemina¬ 
tion with centrifuged or with cooled 
liquid, and so it was desired to use the 
fertile females for insemination. There¬ 
fore the true percentage of success for 
the natural-service type of breeding 
where the liquid was withdrawn is 
considerably higher than the figure 
given. The very low percentage of 
success where the fluid was cooled for 
some time before insemination brings 
down the percentage of success in the 
total inseminated, and in the insemi¬ 
nated but not centrifuged much lower 
than it should be in comparison to the 
Table VIII .—Relation of type of breeding to success in inducing pregnancy 
Type of breeding 
Failed 
Suc¬ 
ceeded 
Per 
cent of 
success 
, . , 
300 
69 
18.7 
Natural serv,ec| Flui(1 washed 01It . 
10 
Normal_| 
i,ncmutea. 
Diluted_ . _ 
31 
4 
0 
11.4 
[Delayed.... 
1 
1 
(Whole sample. 
...<Inside sample. 
4 
0 
Undiluted— 
30 
4 
11.8 
Inseminated— 
Centrifuged_ 
1 Outside sample. 
(Whole sample. 
-- 1 Inside sample. 
23 
1 
9 
0 
28.1 
Diluted_ 
172 
35 
16.9 
1 Outside sample. 
157 
36 
Held some time at ab-' 
normal temperatures/ 
[(’old. 
(Undiluted.. 
■■■(Diluted..-. 
(Undiluted. 
-■■(Diluted. 
79 
3 
3.7 
8.3 
Warm. 
23 
1 
Total undilutec 
6 
190 
0 
21 
10.0 
Total diluted..... 
397 
76 
16.1 
14.3 
19.7 
17.8 
Total natural services with semen removed.. 
Total centrifuged. .. 
310 
387 
76 
84 
Total inseminated hut not. centrifuged__ 
201 
14 
6.5 
