308 PROPERTIES CONFERRED BY COLLOIDAL CONSTITUENTS 



The fact that acids greatly increase the swelling-capacity of Gelatin 

 or Fibrin has led M. H. Fischer to attempt to account in this way for 

 the edematous conditions of tissues which are encountered in a variety 

 of pathological conditions. He is of the opinion that the Edema of 

 tissues is due to local development of acids which increase the affinity 

 of the tissue-proteins for water. Many objections to this view have, 

 however, been advanced by a number of investigators and it does 

 not appear feasible to account for the phenomena of edema in any 

 such simple manner. In the first place the buffer-action of the tissues 

 and tissue-fluids must undoubtedly prevent the development of a 

 sufficiently high acidity to account for the accumulations of fluid 

 which occur in edema. The acidity required to influence in so decided 

 a manner the swelling of gelatin or fibrin, is far greater than the acidity 

 which could possibly prevail within living tissues or the tissue-fluids 

 derived from them, and as a matter of fact very considerable edema 

 may prevail in tissues displaying no perceptible deviation from the 

 normal neutral or excessively faintly alkaline reaction of all living 

 tissues and tissue-fluids. Then, again, the accumulations of fluid 

 which occur in and characterize edema are more frequently interstitial 

 than intercellular. The fluid is found between the cells and not within 

 the cells themselves, where the proteins are present in highest concen- 

 tration. It appears more probable that in the majority of the instances 

 of edema, fluid accumulates in abnormal situations because the per- 

 meability of the membranes lining the lymph-spaces or finer blood- 

 vessels has been increased by injury. Thus we know that various 

 substances such as leech-extract or extracts of shell-fish or peptones, or 

 other injurious agencies such as heating, will so greatly modify the 

 permeability of the capillary bloodvessels as to lead to great accumula- 

 tions of fluid in the lymph-spaces. Similar changes in these or other 

 membranous surfaces may very probably account for the accumulation 

 of fluids in the cellular interstices of tissues in certain disease-conditions. 

 Even when edema is accompanied by the accumulation of fluid within 

 the cells themselves, this is rather to be attributed to alterations of 

 permeability or of the affinity of the proteins for water by disturbance 

 of the normal balance of the inorganic salts in the protoplasm, than to 

 local development of acidity. 



REFERENCES. 

 GENERAL: 



Hoeber: Physikalische Chemie der Zelle und der Gewebe. Leipzig, 4th edition. 

 Robertson: The Physical Chemistry of the Proteins. New York, 1918. 

 EMULSIONS AND SURFACE-TENSION: 



Quineke: Pflliger's Arch., 1879, 19, p. 129. Drude's Annalen, 1901, 7, p. 631; 



1902, 9, p. 969; 1903, 10, p. 507. 

 Billschli: Untersuchungen iiber mikroskopische Schaume und das Protoplasma. 



Leipzig, 1892. 

 Ramsden: Arch. f. Anat. u. Physiol., Physiol. Abt., 1894, p. 517. Zeit. f. physik. 



Chemie, 1904, 47, p. 336. 



Hardy, W. B.: Jour. Physiol, 1899, 24, p. 158. 

 Rona and Michaelis: Biochem. Zeit., 1907, 5, p. 365. 



