Prevention of Innominate Bone Separation During Pregnancy in the Mouse. ∗

Abstract

Summary

The innominate bones in virgin mice of the Brown-belt strain were tied together at the pubic symphysis with silk thread. This was done to prevent innominate bone separation and concomitant enlargement of the birth canal during pregnancy. The females were then mated. Each pregnant mouse gave birth to normal living young at the usual time even though its birth canal was not enlarged during pregnancy by innominate bone separation at the symphysis. All of the pelvic joints became flexible, including the symphysis. Although the tied innominate bones remained closely approximated at the symphysis the pre-pregnancy symphysial cartilage was replaced by ligamentous tissue.