462 



DISCOVERY REPORTS 



Table 29. Calculation of average annual rate of ovulation. Three 2-year periods are considered, beginning 

 with a post-partum oestrus (a), a post-resting oestrus (b), and a post-lactation oestrus (c). See text for 

 explanation 



ioo% post-partum ovulation 80% post-partum ovulation 



1. 

 2. 

 3- 

 4- 



5- 



Multiple ovulations (3 %) 



Annual rate of ovulation 



2-947 

 0-088 



3-Q35 

 i-5i8 



2-927 

 0-088 



3-QI5 

 1-508 



2-891 



0-087 



2-978 

 1-489 



2-729 

 0-082 



2-811 



1-406 



B. Beginning with post-resting oestrus 



1. Winter (post-resting) 100% success 



2. Winter (post-partum) 



3. Summer (post-lactation) 5 % success 



Multiple ovulations (3%) 



Annual rate of ovulation 



2-910 



0-087 



2-997 

 1-499 



2-820 

 0-085 



2-905 

 J -453 



2-730 

 0-082 



2-8l2 

 1-406 



2-710 



0-081 



2-791 

 1-396 



C. Beginning with post-lactation oestrus 



1. Summer (post-lactation) 5% success 



2. Winter (post-resting) 100% success 



3. Summer (post-partum) 



4. Winter (post-lactation) 100% success 



5. Winter (post-partum) 



Multiple ovulations (3 %) 



Annual rate of ovulation 



Total 

 Average 



4-56o 

 1-520 



4-5°2 

 1-501 



4-434 

 1-478 



4-242 

 1-414 



2-690 

 0-081 



2-771 

 1-386 



2-620 

 0-079 



2-699 

 !-35o 



4" J 74 

 i-39i 



2-637 

 0-079 



2-716 

 1-358 



2-530 



0-076 

 2-606 

 1-303 



4-097 

 1-366 



This procedure has been followed for the other assumed rates of post-partum ovulations and post- 

 partum conceptions, and the resulting annual values are averaged. The six mean values finally obtained 

 vary from 1-366 to 1-520, which means that if the assumptions cover almost all the possible range of 

 variation in the incidence of ovulations, the annual rate is between about 1-35 and 1-55. Some of these 

 assumptions are considered to be more likely than others ; it is thought to be probable that the incidence 

 of post-partum ovulations lies between 80% and 100% (probably nearer to 80%), and that the propor- 

 tion conceiving at this ovulation is about 18%. Taking the average of columns 2 and 5 in the final 

 line of Table 29 gives a figure which meets these conditions and suggests an average annual rate of 



