126 EXUDATIONS. 



connexion between the quantitative relations of the exudations and 

 the mechanical conditions necessary for their formation. 



Perfect as in many respects the phenomenology of the exu- 

 dative process may be already considered, obvious as are the 

 mechanical conditions which give rise to exudation as well as to 

 transudation, and great as have been the advances made in our 

 endeavours to trace the laws by which the most minute fluid 

 particles distribute themselves through membranes or through 

 other fluids, and strive reciprocally to establish themselves in a 

 certain equilibrium, we can yet never expect to obtain an inductive 

 proof for our mechanical hypotheses until we can succeed in 

 making the quantitative composition of the products of these pro- 

 cesses harmonize with the laws or provisional hypotheses which 

 we have elsewhere endeavoured to establish. The labours of some 

 of the most distinguished physiologists have afforded us consider- 

 able insight into the knowledge of the phenomena which exhibit 

 themselves both around and within the capillaries during the 

 existence of the inflammatory process which precedes the exuda- 

 tion. The disturbances of the circulation, whose hydraulic laws 

 have been traced even in the smallest of these tubes, have not 

 yet been followed to their individual controlling causes, and much 

 difference of opinion still prevails in relation to this subject ; but 

 there is no lack of elements having a physical basis which may serve 

 to explain these phenomena. In close connection with changes in 

 the modulus of elasticity of the capillary walls there are a number 

 of phenomena which we may very frequently show, with almost 

 mathematical exactness, to be mechanically necessary consequences 

 of these changes. We would here merely indicate, amongst the 

 most recent investigations relating to physiological mechanics, the 

 able inquiries of Jolly* and Ludwigf on endosmosis and endos- 

 motic equivalents, C. Schmidt'sf experiments on the relation 

 between the coefficients of density and equivalents of diffusion of 

 saline solutions, and Graham's remarkable discoveries in relation 

 to the diffusion of dissolved substances. If to these we add the 

 recent classical investigations of Volkmann||, and E. H. Weber^f on 

 hsematodynamics and the well-known investigations of Du Bois 



* Zeitsch. f. rat. Med. Bd. 7, S. 83-148. 



f Ibid. Vol. 8, pp. 1-52. 



I Charakteristik der Cholera. S. 22-28. 



Ann. d. Ch. u. Pharm. Bd. 77, S. 56-89, u. 129-160, [or Phil. Trans, for 

 1850, p. I]. 



|| Die Hsomodynamik nach Versuchen. Leipzig, 1850. 



^J Ber. der k. sachs. Ges. d. Wiss. 1850, S. 164-204. 



