1424 Journal of Applied Microscopy 



ance of a certain quantity of blood in a standard cell was compared by the 

 " telephone method " with a known resistance on a rheostat. The results are for 

 convenience expressed 10,000 times greater than their absolute value in 

 Kohlrausch units. It was found that the conductivity of defibrinated ox blood 

 was from 52.50 to 70.89, while an equal amount of serum alone showed a con- 

 ductivity of from 114.40 to 131.08. Furthermore the conductivity of a .7 per 

 cent, solution of NaCl under similar conditions was 124.10, very nearly the mean 

 value for the serum determinations ; thus indicating in another way that such a 

 solution of NaCl is a " physiological normal " solution. The degree of dissoci- 

 ation of the serum electrolytes was determined to be about .65 to .76. It was 

 found that between 20° and 40° C. the conductivity rises with the temperature. 

 There is no difference in the conductivity between arterial and venous blood. 

 The electrolytes of the blood corpuscles contribute very little to the carrying of 

 the current while they are in the corpuscles, but as soon as they diffuse out into 

 the serum they become active. From this it follows that by measuring the con- 

 ductivity of both serum and corpuscles a method is given whereby it may be 

 determined what quantity of an electrolyte added to the blood has entered into 

 the corpuscles and how much has remained in the serum. The conductivity of 

 the blood is not simply proportional to the serum content, but is considerably 

 influenced in some way by the resistance of the corpuscles present. 



To determine precisely this effect of the suspended corpuscles on the con- 

 ductivity of the whole blood is the purpose of the second paper in the series. A 

 large number of experiments were performed to test the effect on the conduct- 

 ivity of solutions of different electrolytes of the- presence of suspended particles 

 of some non-conductor, as for example sand grains. The solutions of the elec- 

 trolytes were made in gelatin, which was allowed to harden and thus hold the 

 sand grains in any desired arrangement. Essentially the same methods of 

 measuring the resistance were used in these experiments as in the preceding in- 

 vestigation. The results show that the electrical conductivity of a solution is 

 mechanically influenced by the presence of non-conducting, suspended particles, 

 and that this influence is, within certain limits, independent of the size of the 

 particles and the conductivity of the solution, but is markedly affected by the 

 amount and arrangement of the non-conducting bodies. Formulas are given 

 by means of which an absolute value for this effect can be determined. From 

 parallel experiments it appears that the blood, in so far as its conductivity is 

 concerned, behaves as an electrolyte in which the corpuscles play the part of 

 suspended non-conducting bodies. 



The third paper in the series discusses the permeability of the red blood 

 corpuscles for different substances. The method used was that which has been 

 indicated above, namely the measurement of the electrical conductivity of the 

 blood after the addition of the substance to be tested. Solutions were made in 

 both water and serum. When potassium chloride, potassium sulphate, or mag- 

 nesium sulphate are dissolved in serum and mixed with defibrinated ox blood, 

 by which process the osmotic pressure of the serum is of course raised, they 

 only enter the corpuscles to a very slight degree. On the other hand, under 

 similar conditions ammonium sulphate and ammonium chloride are taken up by 



