Abstract
The occurrence of intrauterine respiratory movements in the foetus has been noted 1-4 but has received scant study.
The use of the method of Snyder 5 to inhibit parturition in rabbits enabled us to make direct observations upon the full term foetus in the unopened uterus. Anesthetization of the abdominal and perineal region was accomplished by section of the lumbar spinal cord under novocain. After partial immersion of the animal in a bath of warm (38°) Ringer's solution, laparotomy was performed, and the foetuses were observed through the transparent wall of the intact uterus. A cannula was inserted under local anesthesia into the mother's trachea to permit administration of various gas mixtures. This report is based upon observations in 30 pregnant rabbits, studied from the 28th to the 34th day of gestation.
Foetuses within the intact uterus exhibit spontaneous respiratory movements characterized by rhythmic excursions of the thorax and abdomen. Although shallower, they resemble qualitatively the respiratory movements observed after birth. There is great variation in respiratory activity among different foetuses in the same uterine horn, some may be quiescent, others respiring at independent rates up to 60 per minute. The rate usually increases during the first half-hour of an experiment and thereafter remains fairly constant.
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