492 ORREN LLOYD-JONES AND F. A. HAYS 
TABLE 6 
, Matings and resulting pregnancies from the various end services 
ist 5TH 10rH 15TH 20TH 
a | & er |b] a RR Vale Ob ie | enw seoea carla anes s 
Sie. |) SR RS BT =n T= fe = Daa lites ese ||| 
Sieteeees | 8 og | Seles le eae | 28) | Saale 
2 Se || JE Spi ar SW SS Sie. oan |e = g 
Simon es | a | euieers Ps) ae sali Mica Og |S aes 
= 3 2 55 | 6 z 58 ° z 58 iS z 54 ° 2 58 
Seeley | 6 B.| & | Be | a | a eB | a | a Be | & | & 
1 17 | 11 |64.70) 9 TANTS CA) 74 6 |50.00) 12 | 6 |50.00) 26 | 10 |38.46 
: 14 | 12 /85.71| 15 | 9 |60.00} 11 6 |54.54; 5 | 2 |40.00 
4 12 | 8 66.66) 12 | 6 |50.00 6 150.00) 12) 4 |33.33) 19 | 6 131.57 
Total] 43 | 31 |72.09) 36 | 22 |61.11} 35 | 18 |51.42) 29 | 12 |41.37| 45 | 16 |385.55 
natural semen the by-products of the metabolism of the sperm, 
and also of the developing bacteria more quickly reach a con- 
centration that is deleterious or even fatal to the sperm. 
Whether the fertilizing power of the sperm is diminished by this 
dilution is a matter for further study. Certainly it is not com- 
pletely destroyed, for Iwanoff reports inseminating rabbits with 
semen diluted with a weak Na,CO; solution, with resulting 
pregnancy. 
CERTAINTY OF PREGNANCY 
In the previous sections of this paper we have shown that ex- 
cessive sexual service causes decrease in amount of ejaculated 
semen, decrease in number of sperm cells per cubic millimeter, 
decrease in the proportion of sperm that show progressive mo- 
tion, and decrease in duration of motion. All these changes are 
such as to reduce the likelihood of such semen causing pregnancy 
of the female. In other words, we should expect the percentage 
of pregnancies induced by the copulations to become less as the 
number of preliminary services increases. This is in truth found 
to be the case as shown in table 6. 
The decline proceeds with fair regularity whether we consider 
the males separately or together. This reduction in the per 
cent of effective matings when the male is sexually overworked is 
recognized by those engaged in animal breeding as one of the 
