The inheritance of a lethal muscle contracture in the sheep

Summary

• 1. A lethal deformity of new-born lambs is described. The most striking feature of the condition is that the lambs are born with some or all of the limbs rigidly fixed, with only a small degree of movement possible at the joints. Parturition is rendered very difficult and there is a considerable mortality amongst the ewes producing these lambs.

• 2. The condition depends upon the homozygous state of an autosomal recessive factor.

• 3. During two years the sex-ratio of the affected lambs born in the flock observed was abnormal. Subsequent results and in particular anad hoc experiment gave a normal sex-ratio. Whether there is an additional complication that can lead to a disturbed sex-ratio must be left an open question.

• 4. The incidence of the defect is discussed and a brief account is given of the history of its appearance in the particular flock observed.