134 EXUDATIONS. 



being homogeneous, but already separated into a coagulum and a 

 fluid. 



The coagulum varies very much in form and colour according 

 to the relations under which it is separated, and the quantity of 

 blood which it contains. The microscopical characters are gene- 

 rally, or indeed principally, the same as those of spontaneously 

 coagulated fibrin, but in addition to the somewhat swollen, almost 

 spherical blood-corpuscles, there occur certain other morphological 

 structures, as, for instance, granules, clots, nuclear structures, and 

 occasionally also cyto'id corpuscles. The coagulum swells in 

 water containing hydrochloric acid as well as in dilute acetic acid, 

 but it does not form a gelatinous mass of such perfect translucence 

 as the fibrin of the blood, or as that of the secretion from a wound. 

 If the coagulum, after having been comminuted and carefully 

 washed, be digested with a dilute solution of nitre, we certainly 

 obtain a fluid coagulable by heat, although some portion of it 

 always remains undissolved in the menstruum in the form of dirty 

 greyish flakes. 



The fluid portion of the more recent plastic exudations is 

 generally clear and transparent ; it only becomes opalescent and 

 turbid after the exudation has remained for some time in the 

 cavity. The reaction is commonly less strongly alkaline than that 

 of the blood-serum ; it, however, coagulates on boiling, not into 

 minute flakes, but generally into curd-like clots, or into a milky 

 or whitish gelatinous mass. The fluid occurring above the curd- 

 like flakes is strongly opalescent, and even whitish ; it passes 

 with difficulty through the filter, which it very quickly obstructs ; 

 it forms, on evaporation, the so-called casein-membranes. Acetic 

 acid does not enable us to detect any casein, and the originally 

 limpid fluid is rendered only slightly turbid on careful neutralisa- 

 tion with acetic acid ; but this turbidity disappears instantly on 

 the addition of a little more dilute acetic acid. The application 

 of rennet only affords negative evidence regarding the presence of 

 casein. The salts and extractive matters differ in no respect from 

 those occurring in the blood-serum. 



The quantitative composition of these exudations, when com- 

 pared with that of the corresponding blood, is far more unstable 

 than that of fresh wound-secretions obtained from animals. The 

 quantity of the fibrin does not even admit of being determined 

 approximately, for independently of the fact that such fibrin 

 (that is to say, the coagulated portion of the exudation) contains 

 insoluble morphological constituents, which cannot be washed 



