202 WILLIAM H. F. ADDISON AND HAROLD W. HOW 



rabbit, which was nearly three weeks pregnant. Three days 

 later the seven young were born, three dead and four alive. The 

 three former had their lungs colored blue, as had also one of the 

 latter. While there is no doubt that liquid is present within 

 the lungs after these inspirations of amniotic fluid, none of the 

 observers have directed their attention especially towards see- 

 ing the contents before such inspirations had taken place. One 

 can easily deduce that liquid is present all the time during the 

 de\'elopment of the fetal lung, but in order to obtain, if possible, 

 direct evidence several simple experiments were performed. The 

 first series was with large sheep fetuses, obtained from an abat- 

 toir, with membranes and uterus intact. In two cases the fol- 

 lowing procedure was followed. The uterus was opened, and 

 the fetus, 35 cm. in length, exposed within the unruptured amni- 

 otic sac. By means of a needle carefully passed through the 

 amnion, a strong ligature was drawn through the tissues of the 

 neck of the fetus, behind the trachea, and out of the amnion 

 again at the point of entrance. With the head of the fetus 

 covered by the amniotic fluid, the ligature was tied tightly and 

 the trachea constricted. Our special aims were to prevent liquid 

 escaping from the amniotic sac and air from entering it. The 

 trachea and lungs were carefully dissected out, without injuring 

 the ^'isceral pleura, and placed in a large jar of water, from which 

 all air-bubbles had been previously removed. After they had 

 been allowed to sink to the bottom of the jar they were agitated 

 in order to remove adherent air. Different parts of the lung 

 were then cut with scissors and crushed. A yellowish-red fluid 

 escaped from the crushed masses of tissue and diffused through 

 the water but no bubbles were seen to escape. 



In a third sheep fetus the trachea was ligated at its upper 

 and lower ends and then dissected out. The closed segment of 

 trachea was carefully cleaned and dried, before being opened over 

 a dry glass plate. It was found to contain a faintly yellowish 

 slightly viscid fluid, which was pressed out on the plate. When 

 this fluid was tested with acetic acid there was a reaction show- 

 ing the ]>resence of mucin. The bronchi contained a similar fluid, 

 and when the lungs were compressed this fluid was forced out. 



