186 Dr. J. F. Halls Dally. On the [Jan. 24, 
VII. The Costo-phrenie Plewral Reflexion. 
According to the surfaces with which it is in contact the parietal layer of 
the pleura conveniently may be divided into costal, diaphragmatic, and 
mediastinal portions. The foldings of the pleura constitute three marginal 
grooves or recesses :— 
1. Pericardio-phrenic groove. 
2. Pericardio-sternal pleural reflexion. 
3. Costo-phrenic pleural reflexion. 
1. The pericardio-phrenie groove is a shallow recess formed at the junction 
of the pericardium with the diaphragm, and lodges the plice adipose. 
2. The perrcardio-sternal reflecion forms the anterior marginal pleural 
recess. 
3. The costo-phrenie reflexion must be considered in greater detail, since it 
facilitates to such a marked extent the action of the diaphragm. It is 
formed by the meeting of the costal and diaphragmatic portions of the pleura, 
and, beginning at the lower border of the 6th rib close to the termination of 
the gladiolus, it passes downwards and outwards, reaching the lateral aspect 
of the spinal column at the lower border of the twelfth thoracic vertebra. 
Practically the limit to which the lung descends in ordinary inspiration marks 
its upper boundary. Here, owing to friction between the pleural surfaces, a line 
of demarcation, best seen in the recent state, indistinct in the young child, but 
increasingly definite with advancing age, gradually forms. If evidences of 
pleurisy are present, not infrequently a ridge of organised lymph, concave on 
its upper surface, delimits the lower lung margin, forming a groove into which 
the lung fits. The lower border of the reflexion is wavy or festooned, the 
festoons being in relation with the intercostal spaces. In a series of 20 male 
and female subjects, of ages varying from 18 to 56 years, who had died from 
causes not involving the lungs, the average depth of the costo-phrenic 
reflexion, measured in the mid-axillary line from lower margin of lung to 
lowest limit of pleural cavity, on the right side was found to be 8°62 cm., 
and on the left side 834 cm. The greatest interval in the series was.11 cm. 
on the right side (corresponding to 9 cm. on the left), and the smallest, 
5 em. on the left side (corresponding to 6 cm. on the right). In a female 
infant aged three months the depth of the reflexion on the right was 1°5 cm., 
and on the left 1:4 cm. 
Function of the Costo-phrenie Plewral Reflexion.—The two serous surfaces 
constituting the reflexion remain in apposition for a distance varying with 
inspiration and expiration, and are not separated until the wedge-shaped 
