The greatest and most marked differences of inflammation are manifested in its products. In inflammations due to a pre-existent crasis, such difference is intelligible enough, the product of the stasis having its germs, in part at least, preformed in the general circulation. It is less clear with respect to inflammations devoid of a pre-existent crasis. Mere local inflammation, however, independent of any dyscrasial materials, will yield products presenting a repetition of many, if not of all, the characters which mark the products of dyscrasial inflammation, such as simple (plastic) fibrinous exudation, fibrino-croupous (pyin-holding) exudation, pus, ichor. Here the question is: wherein are the different characters founded? how elicited by stasis out of normal matter? Their ultimate source can be no other than the stasis itself, of which it might be predicated -

(a.) As stasis it promotes, and, within its range, condenses upon inconsiderable elementary materials, the changes and formative processes which take place in the general circulation.

(5.) When feeble in intensity it determines mechanically the display of thin, serous, sero-fibrinous, sero-albuminous substances, poor in plastic materials.

(c.) Greater intensity and duration occasion relatively, through the continued afflux of oxygen to a given quantity of plasma engaged in stasis, excessive fibrin formation, and ulterior oxidation of the fibrin. Hence result fibrinous exudation, and, as a higher degree of oxidation of the protein (Mulder), croupous constitution of the fibrin, croupous exudates, pus- and ichor-exudates.

(d.) Absolute stasis, deficiency of oxygen, leads to necrosis of the blood and of the implicated textures, - gangrene.

The exudate is, accordingly, now of general, now of local import. Exudates, when formed, suffer various changes through external influences, and take various impressions not inherently theirs; thus not unfrequently entering upon anomalous modes of development. Like blastemata, they do not exude unalloyed; croupous fibrin and pus, for example, being always mingled with a certain amount of so-called plastic fibrin and normal plasma. Nevertheless, the study of exudates in their utmost simplicity of forms is indispensable.

Exudates, indeed, both in their primitive condition, and in the changes which they undergo, irrespectively of impressions from without, afford an insight into the local processes occurring in blood involved in stasis, as also into the processes carried on in the general circulation, that is to say, into the crasis itself.

The most instructive of all exudates are those occurring upon serous and mucous membranes, upon which many, if not most, crases are wont to localize.

The doctrine of inflammatory exudation is, in many points, applicable to the products of other processes of exudation, nor shall we, in the sequel, neglect the opportunity of generalizing in this sense.

Let us pass, in the mean time, to the enumeration of exudates as established according to anatomical research, taking at the same time, a general survey of the various changes which they undergo.

1. Fibrinous exudation comprises several varieties, each corresponding to a particular constitution of the fibrin of blood involved in stasis, or of the general circulation. They are, for the most part, not pure, one kind being always alloyed with a proportion, however minute, of another kind, and a certain amount of normally constituted fibrin attaching to all.