312 



COLLOIDS IN BIOLOGY AND MEDICINE 



Within the physiological limit of 3 to 6 volume per cent CO 2 , the 

 concentration of H ions in the blood varied only from about 0.35 to 

 0.75 X 10~ 7 . When the content of C0 2 is greater, we shall see that 

 the H ion concentration may rise. According to H. LoEWY,* 1 the 

 normal CO2 content in the alveoli on closure of the air passages may 

 increase from 5 per cent to 13.4 per cent, which produces approx- 

 imately 50 per cent increase in the concentration of H ions. 



A. SZILI * injected rabbits and dogs intravenously with hydro- 

 chloric acid and found shortly before death an H ion concentration 

 of 9 X 10~ 7 ; in diabetic coma H. BENEDICT* observed a p H value of 

 1.5 X 10- 7 . 



This increase in the H ions is doubtless associated with an in- 

 creased viscosity of the plasma. We shall see that this is vanishingly 

 small, hardly measurable in proportion to the increase of the vis- 

 cosity of the blood which an equal concentration of H ions produces 

 through a swelling of the red blood corpuscles. 



The viscosity of .the total plasma does not teach us anything about 

 its viscosity at the interface between tissue and blood. The friction 

 at this surface is absolutely determinative for the circulation of the 

 blood. 



What are the conditions at these surfaces? The blood is neutral, 

 the tissues are acid. In the cells there is an oxidation which passes 

 by way of the most diverse fatty acids to carbonic acid. The fatty 

 acids involved are without exception stronger acids than carbonic 

 acid. Accordingly, at the interface tissue/blood, an ionization of 

 the albumin must occur and with it an increase of the friction. The 

 friction must be greater in proportion to the disturbances of the oxidiz- 

 ing processes in the cells; i.e., the less oxidation to CO 2 , the faintly acid 

 end product, the more acids with high dissociation constants are 

 formed. The friction at the boundary, i.e., the albumin ionization, 

 becomes great also when the blood itself is saturated with C0 2 , that is, 

 when the products which diffuse into the blood from the tissues have 

 less alkali to combine with than normally. 



