The authors investigated in detail the serum-formolized erythrocyte system in which the agglutino-sedimentation (Rubino phenomenon) takes place. Each phase of this system is investigated from the physico-chemical view point. The authors took advantage of the data obtained for the elaboration of an analogous system with its proper parameters, different from those established by Rubino. As evidence of the phenomenon the aspect of the globules mass sedimented after 24 hours at ± 10ºC (Sedimentary Hemodispersion) was choosen instead of the agglutino-sedimentation rate. The new proposed technic, systematically applied allowed the authors to draw the following conclusions: a) there is no "specificity" correlated to diseases; b) the phenomenon in question results from the combined activity of gammaglobulines as dipoles, positive ions in the medium and propitious polarity of the formolized erythrocytes; c0 the raise of seric gammaglobulines, especially those with isoeletrical point at same level as blood pH, is responsable for the phenomenon, independently of the morbid cause that originated the hypergammaglobulinemia; d) mainly in lepromatous leprosy, in increase of the mentioned gammaglobulines is very frequent and lasts a long time even after clinical regression of the disease An explanation for such fact is suggested; e) the authors have repport also an special activity of the formaldehyde upon the reacting sera and build up a hypothesis for this fact.