PRENATAL AND NEONATAL LUNG 201 



METHOD OF PRESERVATION OF MATERIAL 



In order to preserve, as nearly as possible, the normal relations 

 of the lung to surrounding structures, and to prevent its collapse, 

 all animals were injected with 5 or 10 per cent formalin, either 

 through one of the umbilical vessels, or through the aorta, with- 

 out opening the thoracic cavity. After the lungs had hardened 

 in situ, portions were removed, embedded in paraffin or celloidin 

 and sectioned. 



CONTEXTS OF THE SPACES \MTHIX THE FETAL LUNG 



When a living fetus, near full-term, is exposed within the 

 uterus, with the amniotic sac still unruptured, it can readily be 

 stimulated to make respiratory movements. The angles of the 

 mouth begin to twitch, and are drawn slightly upwards, the 

 abdomen enlarges, evidently due to the descent of the diaphragm, 

 and almost simultaneously the nostrils dilate, and the mouth 

 slightly opens in a yawning manner. The result is the drawing 

 into the respiratory tract of the amniotic fluid. We found that 

 the mere manipulation necessary to expose the fetus is sufficient 

 to bring about these movements, if the animal is very near the 

 end of gestation. A surer method is to clamp the umbilical 

 cord, but neither method will act if the animal is not sufficiently 

 advanced in its development. Several have previously recorded 

 the above or similar observations. Winslow is quoted by Preyer 

 as having written in 1787, ''Liquorem amniirespirare videntur." 

 Leclard ('15) clamped the neck of a still living fetus, and on 

 opening the trachea found there a fluid analogous to amniotic 

 fluid. When a colored fluid had been injected previously into the 

 amniotic fluid that in the bronchi was likewise colored. Preyer 

 ('85, p. 148) repeated and verified Leclard's experiment with a 

 guinea-pig near the end of gestation. He found that the fuchsin 

 which he injected into the amniotic sac not only colored the 

 lips, tongue, palate and all the pharynx, but also the lungs and 

 the inside of the stomach. Geyl ('80) added to the experiment 

 in the following manner. With all aseptic precautions, he in- 

 jected aniline blue into the amniotic sacs of seven fetuses of a 



