PLETJKISY. 585 



consideration from the practitioner, and must be studied in its chemical 

 and physical composition as well as in the quantities in which it 

 occurs.. 



"1. Chemical Composition. As a direct product of the pleuritic 

 exudation, it consists of the same elements as the blood viz., fibrin, 

 albumen, salts, extractive matter, and blood; but these principles are 

 not always to be found in the same proportions, and some of them 

 appear with peculiar characters, and under various forms, interesting in 

 a pathological point of view. The extractive matter and salts are of 

 less interest; water is in a proportion varying from 911 to 924 in 1000. 



"A Ibumen is constantly present; it is detected by treating the fluid 

 by ether, alcohol, or an acid, and more especially by nitric acid. In 

 four analyses, M. St Cyr and M. Boiteux found it from 73'54 82'50 

 63-3381 parts in 1000. 



"The liquid at this period, left at rest in a glass at a low temperature, 

 separates into clot and serum, in the same manner as the blood. 



"The quantity of fibrin thus obtained has been found in four analyses 

 to vary from 2-1612-50 6'00 7.34 in 1000 parts. 



"The fibrin, however, in this state, is not chemically pure, but shows, 

 notwithstanding, the considerable oscillations which may occur in 

 various samples. 



"Fibrin, which constitutes the basis of the pseudo-membranous 

 productions, is found in variable proportions, and in two different 

 forms: 



" 1st, As long as the febrile state is persisting to a great extent, the 

 fibrin coagulates, and is found as molecular granulations, amorphous 

 particles, parts of false membranes, either resting against the pleural 

 surface or in suspension in the liquid in one word, in a state, more or 

 less advanced, of disaggregation, but not forming a distinct clot. 



"2nd, As soon as the inflammation subsides, and passes to a sub- 

 acute or chronic state, the fibrin coagulates more slowly, and is even 

 for a long time in a state of solution, and in considerable proportion in 

 the liquid contained in the serous cavity. 



" 2. Physical Aspect. At the beginning of the inflammatory state, a 

 plastic lymph, containing a large proportion of coagulable fibrin, 

 escapes from the modified capillaries. Part of it adheres to the pleura, 

 another part gravitates at the bottom of the thoracic cavity. The 

 rupture of some capillaries allows the blood to escape, and the globules 

 impart to the fluid a port-wine colour, sometimes almost black. Some- 



