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



proves and lives. As is known from both clinical medicine and 

 exjierimental studies, the lung has a marked capacity for the 

 absorption of liquids, and the quantity of fluid present in normal 

 birth is readily disposed of. 



AL\TERIAL FOR BREATHIXG AND XON-BREATHIXG LUNG 



In order to secure examples of the breathing and non-breath- 

 ing lung which would be strictly comparable, we used pregnant 

 dogs near the end of the gestation period. By the manner de- 

 scribed in experiment on the contents of the prenatal lung, some 

 of the fetuses were removed and not allowed to breathe. Others 

 were removed from the membranes as quickly as possible, before 

 any attempt at breathing had been made. After the umbilical 

 cord was tied and severed, they were laid in a warm place. They 

 soon showed signs of activity, crying and crawling about. These 

 were etherized at the end of an hour, and injected with formalin. 

 Fetal material was also obtained by etherizing the parent ani- 

 mal after several fetuses had been taken out and allowing the 

 remainder of the young to die before removing them. For com- 

 parison with the new-born, pups two days old were used, and 

 these were injected with formalin through the abdominal aorta. 



STUDY OF PRENATAL LUNG 



The appearance of sections from the fetal lung obtained in 

 the above described manner is shown in figures 1 and 2, The 

 texture of the organ is quite gland-like, with the mesenchyme 

 framework present in large amount. The spaces are variable in 

 size and shape on account of the structures being cut in different 

 planes of section, but the distribution of the spaces is fairly 

 uniform. In order to study the relative area occupied by lung 

 tissue and the intervening open spaces, drawings were made with 

 the Edinger drawing apparatus, on cross-ruled millimeter paper. 

 Various magnifications were used, varying from 60 to 220. The 

 results of a series of such drawings showed that the percentage 

 of area occupied by lung tissue was 70 to 80 per cent and by the 

 intervening spaces 20 to 30 per cent. In view of this condition 

 it does not seem correct to call the fetal lung 'solid,' as do some 



