Elastin fragmentation in the pulmonary artery of the newborn rabbit

Pulmonary arteries of rabbits aged 1 day to 2 months were distended at 44 mm Hg pressure and sectioned for study with the light microscope. Photographs were enlarged, and the frequency distributions of elastin lengths obtained at different ages. Maximum fragmentation occurred in the inner third of the artery, and was most marked at 3 weeks of age. No significant growth, or change in number of elastin lamellae occurred at this age. The fibres tended to be circumferential except in rabbits 4 weeks of age, where they were slightly helical.