The theoretical part of the thesis deals with the explanation of the actions that occur during the stimulation of tissues with the electric current. A significant analogy with electrical circuits is used to describe the phenomena at the molecular and cellular level. The models of membrane and cell are necessary for understanding the behaviour of more complex structures, such as tissues and organs. A considerable attention is paid to the conditions of electrical stimulation which bring about response in the stimulated area. Next, the cumulative effect of the subthreshold stimulation is analysed. The mechanisms of common treatment effects of the electrotherapeutic methods are outlined. The research results in the practical part of the thesis – the design for a microstimulator. Properties of the microstimulator and compliance with standard requirements are verified by testing the electromagnetic compatibility and electrical safety, conducted by the Institute for testing and certification, JSC. The effects of microstimulation on living organisms are experimentally investigated on horses, in collaboration with the Veterinary and Pharmaceutical University. For the first time, thermodynamic sensors are used for the objective assessment of the microstimulation therapeutic effect. These miniature sensors are placed on the horse´s front legs and monitor the changes in thermal activity while only one limb is really stimulated and the other is just considered as a reference. Comparison and statistical evaluation of the measured signals could provide a more detailed view of the thermal changes within the stimulated area, which is significantly related to blood circulation in limbs, and with the support of the reduction of edema. The course of the experiment which deals with the effect of microstimulation on edema of the horse´s legs caused by minor injuries (tendinitis, sprains, etc.), is documented in photographs or videos that are significant for possible evaluation of the effectiveness of the stimulation in this application.