This article studies the lymph flow, the composition of the lymph and blood in acute peritonitis caused by fecal injection. Experiments have shown that acute peritonitis causes a decrease in lymph flow, shifts in the physicochemical parameters of lymph, blood plasma and urine. With fecal peritonitis in animals, an increase in the viscosity of lymph and blood in 28% and 33% in relation to the norm is characteristic. The blood clotting time in rats with peritonitis was observed within 2.79 ± 0.02 min, and in the lymph, it was 3.24 ± 0.04 min. A change in the rheological parameters of lymph and blood occurs simultaneously with a violation of the coagulation system. Clotting accelerated, which worsened the fluidity of both blood and lymph. An analysis of our results also shows that a decrease in the volumetric rate of lymph flow corresponds to a change in not only biochemical, but also physical properties of lymph. The content of electrolytes in the studied biological fluids changed.