Serous and Fibrinous liifhuiiinatious. 273 



the body). The exudate may exist in the lymph spaces of the tissues, 

 fining them completely (infiltration), or may escape to the surfaces, 

 where it forms a deposit upon the latter ; it may collect in the body 

 cavities or may find free exit from the body. Even in normal con- 

 ditions leucocytes find their way between epithelial cells, and when 

 the epithelial tissues are loosened in inflammation or actually des- 

 quamated the exudate is given easy access to the free surface. The 

 qualitative composition of the exudate is by no means uniform ; 

 sometimes the major portion is plasma and cells are but scantily 

 met in it, sometimes the reverse is true. In addition admixtures of 

 tlie secretions of organs may be found present, or products of tis- 

 sue disintegration or changes due to coagulation, putrefaction or 

 inspissation. all of which serve to give a very variable character to 

 the exudation. 



The terms serous exudate and serous inflammation are employed 

 in connection with an aqueous product of inflammatory extravasa- 

 tion : the fluid is rich in albumen, like the serum of the blood, lim- 

 pid or slightly clouded, of a yellow wine tint, or sometimes red 

 from the presence of erythrocytes. When it soaks through a tissue- 

 and gives it a juicy gelatinous appearance the structure is said to be 

 the seat of iiif^aiiiinatory a^ieuia; collecting in the sacs of joints, 

 tendon sheaths and the serous cavities the expression inflammatory 

 dropsx is applied. In the skin surfaces, which are covered with 

 squamous epithelium, the upper layers of which are but slightly 

 permeable for fluids, it may collect in the more easily penetrated 

 deeper layers of the rete ]\Ialpighii and raise up the superior strata 

 to the formation of blisters. In mucous membranes the fluid passes 

 through the epithelial layer and mingles with the physiological secre- 

 tion and the desquamated cells of the membrane, escaping with 

 these ; in this case the term catarrhal exudate (Karap^o}. to flow 

 away) is employed. Such catarrhal exudate may be very thin and 

 water like, or may be viscid. The irritation of the inflammatory 

 condition invariably induces an increase of secretion (increased flow 

 of tears, increased secretion of nasal mucus). 



It is said to be a fibrinous exudate in case the exuded fluid under- 

 goes coagulation by precipitation of fibrin. This form is met par- 

 ticularly on the free surfaces of serous membranes and mucous 

 membranes, within joints and in the lung, and to a less degree in 

 the meshes of the tissue. Coagulation occurs in case the fibrin 

 forming substance, which is always abundantly present in every 

 exudate, comes in contact with fibrin ferment, the latter being sup- 

 plied by necrosing cells, especially leucocytes and endothelial cells. 



