X-ray Studies of the Closing of the Ductus Arteriosus

Abstract

1. A technique is described by means of which serial radiographs of the ductus arteriosus of the full-term lamb, delivered by Caesarean section, were obtained over periods ranging from 25 seconds to 33 minutes after delivery. 2. The radiographs so obtained show that:— (a) There were marked differences between the pictures obtained in vivo and those revealed by post-mortem dissection. (b) Functional closure of the ductus had occurred in every case within a minute from delivery, and even when the vessel was patent the flow through it appeared to be sluggish. (c) This functional closure was not effected by a rapid and simultaneous contraction of the total musculature of the ductus, but through the independent and intermittent activity of groups of muscle fibres, leading to twisting and kinking of the vessel. Consequently, the calibre and course of the ductus changed continuously from moment to moment throughout the periods recorded. The formation of beads of the opaque medium within the lumen was a striking f...