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Scientific Proceedings (128) 



one of the authors 1 showed the fluid coming in from the tissue 

 spaces was almost pure salt solution having a protein content of 

 only 0.6 to 2 per cent. If changes in the concentration of the 

 plasma could be shown when the blood becomes concentrated in 

 corpuscles, it would get away from all objections of hidden 

 masses of corpuscles. 



In the experiments recorded here the concentration of injected 

 congo red has been followed in the plasma. This method is not 

 ideal for all phases of this problem because there is normally a 

 gradual decrease in its concentration. Thus, according to Harris, 2 

 considering 100 as the percentage after the dye has been uni- 

 formly mixed with the plasma there is a fall of about 4 per cent, 

 in five minutes. This is however, slower than with vital red. 

 This figure is not fixed and sometimes we found larger figures 

 than that and sometimes less. If, after this second sample of 

 blood has been taken, the blood pressure be raised by the in- 

 jection of adrenalin or by section of the vagi and a third sample 

 taken after a few minutes, one finds the concentration of congo 

 increased. Thus, in one instance nineteen minutes after injec- 

 tion of congo and fourteen minutes after the first sample of blood 

 containing congo had been taken we have found 111 per cent, 

 of congo in the plasma as a result of adrenalin. This was in an 

 18 kilo. dog. The dog had about 693 c.c. plasma to commence 

 with and this would mean about 63 c.c. of fluid had left the blood 

 provided no congo had left in the time. Because congo is leav- 

 ing the blood all the time the method of following dyes can give 

 only relatively crude figures, but they show such results as were 

 obtained by one of the authors 3 when the haemoglobin change 

 was followed, are due to fluid leaving the blood and not to hidden 

 masses of corpuscles. They indicated that the colloid of the blood 

 does not leave the blood as fast as the water. The changes in 

 the concentration of the natural colloid of the blood are being 

 investigated. 



1 Journal of Physiology, 1916, 1, 157. 



2 Brit. J. Exp. Path., i. 162. 



8 American Journal of Physiology, 1917, xliv, 298. 



