ipii] William J. Gies 303 



as far as the outer wall of the capillaries. If we try to aid Cohnheim's 

 conception of permeability and make it extend to all protoplasm, then 

 we are getting the cause of our edema right where we have tried to 

 say it is, namely, in the tissues themselves ; and then our problem is 

 simply that of how tissues hold their water. In this the forces that 

 have been suggested as active — not only the variable affinity of colloids 

 for water, but the previously suggested osmotic pressure, with or with- 

 out Overton's conception of lipoidal surface layers — are so infinitely 

 greater than the highest grades of blood pressure that pathologists 

 have ever registered that the two cannot be compared. (Page 207.) 



The more recent experiments of Magnus have added much to our 

 knowledge of the experimental side of edema. His results, too, are 

 usually interpreted as lending support to Cohnheim's conception of the 

 increased permeability of bloodvessel walls as a factor in the produc- 

 tion of edema. How well they support the belief that the cause of 

 edema is to be sought in a change in the colloidal Constitution of the 

 tissues is readily evidenced by the following. Magnus found that 

 animals which are transfused after death always develop a general 

 anasarca. Living animals do not do so as readily as the dead, but they 

 do it readily if deeply chloroformed or etherized or injected with 

 arsenic. In place of these words we could write, placed in a condition 

 of lack of oxygen with an adequate supply of water. Magnus also 

 found that animals which have their kidneys removed develop an edema 

 if injected with sodium chloride Solution a day or two after the Opera- 

 tion. This is because at the end of this time the tissue colloids have 

 either directly or indirectly been so altered by the metabolic products 

 which should have been excreted through the kidneys that their affinity 

 for water has been distinctly increased. (Page 208.) 



It is readily apparent that through experimental analysis the part 

 played by the blood and the lymph circulations has gradually become 

 less prominent. From having been looked upon as alone determining 

 the amount of water held by the tissues, we have come to find that the 

 tissues are largely their own masters in this regard. The blood and 

 lymph circulations carry fluid to the tissues and away from them, but 

 what the tissues will take off or give off rests with them. Only as these 

 circulatory Systems carry to the tissues substances which directly 

 threaten their existence, or fail to remove such as the tissues have pro- 

 duced, which if allowed to accumulate will overcome them, only in so 

 far are the circulatory Systems masters of the tissues. (Page 208.) 



Of this possible role of the tissues pathologists have not all been 



