The experimental research and theoretical modeling of average radius and refractive index change of spherocytes aggregation of ill and well people under the swelling in solutions of various osmolarity and by taking into account the rigidity of the erythrocyte membrane have been carried out. The spasmodic character of decrease of spherocyte radius has been discovered for the first time. It took place under an NaCl concentration on the order 0.50 - 0.35%. The correlation of the erythrocyte membrane rigidity with a 'jump' value and its position has been demonstrated. The experimental researches of the refractive index have confirmed the spasmodic model of change to the spherocyte radius.