138 EXUDATIONS. 



and the coagulated fibrin slowly dissolved in the originally only 

 slightly modified exudative fluid or in a serous fluid which is 

 afterwards separated ; in the second case, the solid part of the 

 exudation hardens, ceases to swell in acetic acid, and becomes con- 

 verted into a horn-like mass ; and thirdly, the exudation is con- 

 verted into true tissue, namely, connective tissue. One might 

 suppose that the fluids remaining in these older exudations, or 

 permeating the newly formed tissues, would exhibit differences 

 which would readily admit of being chemically distinguished ; but 

 although these fluids certainly exhibit differences of composition 

 on analysis, my observations at all events have failed to detect any 

 definite constitution for any one special alteration of the exudation. 

 We are still deficient in any more careful investigations for showing 

 the character and composition of those forms of exudation, which 

 tend towards the formation or regeneration of specific tissues (such 

 as cartilaginous substance, osseous substance, &c.). 



Croupous exudations. It is only in rare cases that we can suc- 

 ceed in subjecting to a chemical examination exudations of this 

 kind whilst still in a perfectly fresh state, that is to say before they 

 have been changed either by different metamorphoses which they 

 have experienced during life, or by decomposition in the dead 

 body. It may be shown with tolerable certainty that these exuda- 

 tions on their first separation are as fluid, and as similar to the 

 blood-plasma as all other exudations ; but they present this pecu- 

 liarity, that when the fibrin has been coagulated, the fluid portion 

 of the exudation is resorbed with such extreme rapidity that almost 

 every effort to obtain it fails. It almost appears in the case of 

 many of these exudations, as if only a kind of fibrinous juice had 

 permeated the walls of the vessels, and had been deposited in a 

 gelatinous form upon mucous or serous membranes. There is often 

 scarcely a trace of blood-corpuscles to be detected in fibrin of this 

 kind, and on rinsing the exudation with water, we obtain only a 

 very small quantity of coagulable matter, and thus lose all hope of 

 being able to ascertain the original composition of the exudation 

 from the fluid enclosed in the coagulum. Then, moreover, it must 

 be observed, that these coagula, or solid exudations, are in general 

 formed gradually, and thus deposited in distinct strata, some of 

 which experience greater alterations than others. However impor- 

 tant it would be to ascertain the composition of these exudations 

 immediately after their separation, the chemist is compelled to 

 admit his entire inability to solve any of the questions which sug- 

 gest themselves in connection with this point, and must direct his 



