Résumé : (1) LiCl increases the viscosity and decreases the rigidity of nucleohistone; NaSCN has opposite effects. (2) The effects of LiCl and NaSCN on the viscosity of amphibian embryo extracts, as observed by Ranzi and his coworkers, seem to be due to the action of these salts on nucleohistone. © 1947 Birkhäuser Verlag.