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



only a few hours. It is exactly between these two classes of 

 individuals that we have sought to study the differences. Kolliker 

 made numerous lung measurements but apparently none directly 

 contrasting the two conditions seen in the prenatal and post- 

 natal lung. ^Miller's ('95) table of sizes of the various air-pas- 

 sages in dogs is from material of one stage only. Concerning 

 the phenomenon of expansion from a more general point of view, 

 there are many observations. For instance, the fact that all 

 parts of the neonatal lung do not expand equally has been recorded 

 a number of times. Dohrn ('91) says that at least two days 

 are required to unfold the lungs completely. Jalan de la Croix 

 ('83), found in the lung of a child which lived seven days groups 

 of alveoli which persisted airless. In dealing with the lung of 

 children which have survived only a few days after birth, there 

 is the possibility, however, of the organ being prematiu'e or 

 pathological, and either of these conditions would affect its expan- 

 sion. The question of the contents of the spaces in the fetal 

 lung has for the most part been referred to only incidentally, by 

 observers interested in premature respiratory movements. The 

 experiments recorded by Preyer ('85) in his "Specielle physio- 

 logie des embryo," are the most definite we have found, and 

 these will be referred to later. 



A complicating factor in studying the appearance of the nor- 

 mal fetal lung is the possible occurrence of intrauterine respira- 

 tory movements. These have been described in the study of 

 living human fetuses by a whole series of clinical observers (for 

 instance, Ferroni '99) and have even been recorded by means of 

 tracings. The current opinion as expressed by Howell ('11) is 

 that the mammalian fetus under normal conditions makes no 

 respiratory movements while in utero. Ballantyne ('02) in his 

 ''Antenatal pathology and hygiene" accepts the results of the 

 clinicians, but says it is doubtful if such movements are strong 

 enough to draw liquor amnii into the lungs. It would also seem 

 from our experiments that if these movements are really similar 

 to respiratory movements, the}^ are not to be compared in point 

 of intensity with the postnatal efforts, and do not affect the 

 structure of the lung to any extent. 



