184 THE FLUIDS, 



III. EXUDATIONS. 



Exudation has been very often confounded and especially by 

 chemists with mere transudation ; from which, however, it is 

 widely different, both histologically and physiologically. Leh- 

 mann, however, admits that while transudation is the result of mere 

 physical agencies, as has been explained (p. 182), exudation is due 

 to vital power. But he limits exudations to inflammation as their 

 producing cause, and admits that their organizability distinguishes 

 them, from mere transudations. 



We cannot restrict the idea of exudation to the inflammatory 

 process alone, however. We equally find organizable elements 

 separated from the blood in cases where there is no inflammation ; 

 and we cannot apply to such cases the term transudation, any more 

 than we can in case of inflammatory exudations. Any organizable 

 fluid spontaneously separated from the bloodvessels, without rupture of 

 their walls, is an exudation, whether it be in the case of repair (in 

 wounds, &c.) without inflammation, or in cases of actual inflam- 

 mation. 



Exudations differ from transudations -first, in regard to the cir- 

 cumstances in which they are formed; and, .secondly, in respect to 

 their constituents. 



1. Transudations are the result of physical agencies merely, and 

 occur upon the natural free surfaces more especially, and while their 

 epithelium is still in a normal state, and in the areola3 of the areolar 

 tissue (p. 181) ; escaping, also, as Wedl suggests, through the walls 

 of the veins. Exudations occur in consequence of some modified 

 action of the vital force, and directly from the capillaries ; and if 

 upon natural free surfaces, in consequence usually of inflammation 

 or irritation of the same. They also elevate and detach the epi- 

 thelium, as is seen in case of vesicular diseases of the skin. But 

 exudations also occur and not transudations upon free surfaces 

 artificially produced ; as in case of wounds, with or without loss of 

 substance. In all cases, indeed, in which repair takes place, or in 

 which new formations (false membranes, indurations, &c.) are pro- 

 duced, exudations occur ; and it is by their organization that the 

 repair or the formation of the new tissue is secured. Moreover, in 

 normal nutrition an exudation of the plastic elements of the blood 

 occurs in the substance of the tissues, and from which the latter are 

 nourished. But this topic is included under the subject of nutrition ; 



