88 PRACTICE OF MEDICINE. 



case is very rare. These diiferent shades of inflammatory redness 

 must not be confounded with the product of simple ecchymosis ; 

 sometimes after chronic diseases, or certain severe fevers, effusions 

 of blood, merely passive, take place on the external surface of the 

 pleura and peritoneum, in the same manner as they are formed under 

 the mucous membranes and under the skin. In the majority of 

 cases, the pleura, red or white, opaque or transparent, is not increased 

 in thickness ; we very rarely find it really thickened. 



2d. Alterations of secretion. — The alterations of secretion pre- 

 sented by the inflamed pleura are more numerous and more varied 

 than its alterations of tissue. The liquid exhaled by the inflamed 

 pleura presents a multitude of varieties ; in some cases, it consists 

 of colourless or lemon-coloured serum, perfectly limpid and trans- 

 parent ; in more common instances, however, albuminous flocculi 

 are observed to float in the limpid fluid. In other persons, there is 

 found a liquid decidedly turbid, of a yellow, green, brown, or gray- 

 ish colour, which is sometimes very thick, and as it were muddy. 

 Finally, after several immediate states, this liquid presents itself 

 under the form of real pus, such as it exists in an abscess. In some 

 rare cases, the pleura is filled with a peculiar liquid, which is neither 

 serum nor pus ; this liquid, usually deposited in compartments formed 

 by false membranes, resembles either animal jelly half liquefied, or 

 honey. Blood may also be eff*used into the inflamed pleura ; but 

 sometimes the red tinge is so slight that it is evidently merely serum, 

 mixed with colouring matter, which constitutes the effusion. In 

 other cases, on the contrary, the pleura is found filled with a liquid 

 altogether resembling the blood which comes from a vein. It cannot 

 be doubted in this case but that natural blood was really exhaled by 

 this membrane.* The different liquids effused into the pleura are 

 always inodorous, unless a solution of continuity of the thoracic 

 parietes, or a pulmonary fistula, establishes a communication between 

 the cavity of the pleura and the exterior. 



^tUfkeriforni fluids sometimes exist in the pleural cavity, either 

 alone, or, more frequently, mixed with a liquid. Their presence is 

 principally ascertained — 1st, by the hissing noise produced at the 

 moment an incision is made into the chest ; 2dly, by the frothy state 

 of the liquid ; 3dly, by opening the thorax in water. In some cir- 

 cumstances, these gases are evidently the product of an exhalation 

 from the membrane ; but most usually they are found in the pleura 

 only when the latter communicates more or less immediately with 

 the bronchi. 



A portion of the liquid exhaled by the pleura naturally tends to 

 concrete and pass into a solid state. Hence the false membranes, 



* Besides, in the case of hemorrhagic pleurisy (hcemothorax), blood may be 

 effused into the sac of the pleura from a wound, by the rupture of an aneurism, 

 by pulmonary apoplexy, or by a passive transudation. 



