

The Pleura. 123 



Yet even here, there is no actual space existing, since the 

 two walls of the parietal layer are in contact, excepting 

 when the margin of the lung descends between them. 

 The lung is entirely free in the cavity of the pleura, ex- 

 cept at the situation of the root of the lung, and at the 

 point where the lung is attached to the side of the pericar- 

 dium by the broad ligament. The broad ligament may 

 be better appreciated, if the thorax of a subject be opened, 

 and the hand introduced into the pleural sac. Under 

 these circumstances, it is found, that the hand will readily 

 pass over the apex of the lung, and then glide downwards 

 over the inner surface, nearly as far as its middle, where 

 it is stopped by the root of the lung. On the outer aspect 

 the hand passes over the external surface and around the 

 posterior border, while below, it can be inserted between 

 the under surface of the lung and the upper surface of the 

 diaphragm. Internally, however, it cannot pass from the 

 anterior border to the posterior border over the inner sur- 

 face of the lung ; there is some obstacle to its progress in 

 this direction, and this obstacle is composed of the root of 

 the lung above, and the ligamentum pulmonalum latum, 

 or broad ligament, below. This ligament is formed by 

 a duplicature of the pleural membrane and reaches from 

 the root above, to the diaphragm, below, and from the 

 lung, externally, to the pericardium, internally. 



Diseases of the Pleura. Pleurisy. In the 

 early stages of this disease, pain, stich-like in character, is 

 felt, due, partly to irritation of the sensory nerves in the 

 inflamed pleura, and partly to the friction of the diseased 

 surfeces. The side affected is kept, as much as possible, at 

 rest, by means of reflex muscular action through irritation 

 of the intercostal nerves, which supply the pleura as well 

 as the intercostal muscles. Reflex action may result from 

 disturbance of the phrenic nerve also, since this nerve sup- 



