. oy y ot Ate. ote. v 
S * - " ~ 
| UNITED STATES DEPARTMENT OF AGRICULTURE 
fey BULLETIN No. 1121 
et cs 
- Washington, D. C. PROFESSIONAL PAPER » December, 1922 
“THE EFFECTS OF INBREEDING-AND 
CROSSBREEDING ON GUINEA PIGS 
ad 
Ill. CROSSES BETWEEN HIGHLY INBRED FAMILIES 
By SEWALL WRIGHT 
Senior Animal Husbandman in Animal Genetics 
Animal Husbandry Division, Bureau of Animal Industry 
CONTENTS 
Introduction ........ “peor Be] Adult Wolght > (.04).'ells Sad 2 fee 
The Inbred Families. .......... 2 | Frequency of Litters .........22-. 25 
Crossbreeding Experiments ....... 2 | Age of Maturity .......... fake! ae 
| Descriptionof Tables .......-.-- 3 | Complete Sterility ........... - 28 
| Allowance for Seasonal Fluctuations. .- 5 | SizeofLitter....... Caleta ee 
Allowance for Heredity ......... 10 | Total Fertilit 
Allowance for AgeofDam ....:.... 12 ee peda (aS! S289 a eee Pe : Hh 
Allowance for Sex ........ Po Se, ae em eR eke ea” fRA 8 
Resistance to Tuberculosis .....+-+-+ $2 
—, gece! Sra : 4 ‘ 3 é : : ne _Early Views on Inbreeding. ....... 33 
The Percentage Born Alive ....... 1¢ | Pre-Mendelian Experiments. .-..-. 34 
The Percentage Raised Among the Young Mendelian Heredity and the Problem of 
RS SO a 18 Inbreeding « 6s icin, 2 aus 2 Bi ae 35 
The Percentage Raised of All YoungBorn. 20 | Mathematical Considerations ...... 39 
NA ee ee ee 21 | Comparison of Results with Theory ... 46 
TS Oe ee ee 22 | Summary and General Conclusions ... 48 
Weight at Weaning ........... 23 | Literature Cited « < \s. <7 s-< tai Seo cee 59 
WASHINGTON 
GOVERNMENT PRINTING OFFICE 
1922 
