1. The increase of conductivity produced by saponin in formaldehyde-hardened blood is due to an increase in the conductivity of the corpuscles (increased permeability of the corpuscles to ions) and not, mainly at any rate, to the liberation of electrolytes from the corpuscles and a consequent increase in the conductivity of the serum. The increase in the permeability of the corpuscles is probably caused by a "corrosive," dissolving, or emulsifying action of the saponin on some non-proteid constituent of the envelope or stroma.
2. In the first stage of the action of saponin on blood (not fixed by formaldehyde) there seems also to be an increase in the permeability of the corpuscles for ions, even before any hæmoglobin has been liberated. The liberation of the hæmoglobin may be secondary to this, owing to the entrance, of water consequent on the disturbance of osmotic equilibrium.
3. Heating the blood to 40° to 45° C. intensifies the laking action of saponin, so that a dose insufficient to cause laking at ordinary temperature may do so when the blood is heated to the temperature mentioned.
4. Pus corpuscles, like red blood corpuscles, are worse conductors than the serum in which they are suspended. Unlike blood corpuscles, they show no preference for NH4Cl as compared with NaCl. On the other hand, the conductivity of pus is increased by the action of saponin, just as is the case with blood, and apparently very much in the same way, that is to say, by an action on the corpuscles and not on the serum. The fixing of the pus corpuscles by formaldehyde does not hinder this action of saponin.