FORMATION OF DM I'll 337 



from the conversion of i)ol3'-.sa('('li;iri(l(',s witli little li^'di'alion capacity 

 into hyclrophilic pentosans and mucilages.'^ 



On the basis of the facts briefly suniniarized above, the proportion 

 of water present in any cell or in anj^ fluid of the body which contains 

 colloids, is assumed to be determined by certain factors, namely (1) 

 the character of the colloids themselves; (2) the proportion and na- 

 ture of acids or alkalies present in the fluids in and about the colloids; 

 (3) the i^-oportion and nature of the salts. All these factors are 

 changeable, and therefore the amount of water present in the cell or 

 fluid varies accordingly. Thus, if a cell through its metabolism de- 

 velops from such a non-electrolyte as sugar (which has no consider- 

 able effect on the water content of the protoplasm), an organic acid, 

 such as lactic acid, which has a large effect in increasing the affinity 

 of the colloids for water, the cell will, presumably, take on more water, 

 perhaps to a degree to cause intracellular edema. The acids diffusing 

 from the cell into the intercellular spaces or into the lymph will 

 cause equally well an increased affinity for water in the colloids here 

 present, leading to intercellular edema. Conversely, neutralization 

 of acids present in a colloidal solution, by alkaline salts brought by 

 the blood, will decrease the affinity of the colloids for water which 

 will escape from the colloids as they shrink. • 



This theory, which introduces a hitherto unappreciated factor into 

 the considerations of lymph formation and edema, is of the utmost 

 importance. It practically eliminates osmotic pressure, also the cell 

 membranes so essential for the efficiency of this force, and in view of 

 the difficulties that have arisen in trying to fit the cell membrane 

 hypothesis and osmotic pressure to many facts of normal and patho- 

 logical biology, an alternative hypothesis is welcome. As pointed out 

 above, the forces involved in the swelling of colloids are so large as to 

 be of great significance, and the amounts of electrolytes necessary 

 to cause considerable variations in colloidal swelling are not more than 

 can be present under normal and pathological conditions; conse- 

 quently the possible influence of colloidal swelhng must be taken 

 into account in all consideration of pathological processes. Whether 

 or not it is capable of as universal application as Fischer mamtains, 

 remains to be demonstrated, and there are,' indeed, some facts that 

 do not seem to be in harmony with this theory. 



Summary. — We see from the above discussion that numerous the- 

 ories have been advanced to explain the normal formation of lymph, 

 and as their basis exist several different possible factors. Filtration, 

 active secretion by the capillary endothelium, attraction by the tissue- 

 cells, osmosis in response to formation of crystalloids outside the ves- 

 sels, and changes in the affi.nity of colloids for water; all have been 

 shown to be possible causes of lymph formation. It is highly probable 

 that in a certain wa}' all are involved, particularly if we accept the 



19 MacDougal and Spoehr, Plant World, 1918 (21), 245. 



22 



