The spontaneous rheumatoid disease in animals is a representative example of all the stages of rheumatism which occur in nature. It is caused exclusively by bacterial, mycoplasmal, or viral infection. The organs involved in rheumatic reactions are characterized by borders between tissue incapable of inflammation, without vessels and nourished by passive perfusion, and highly reactive, well vascularized connective tissue. By this combination microorganisms are deposited on the one hand, and then later the appearance of immune complexes is possible. These settlements are sustained by the initially occurring coagulation and permeability processes of the infection in the "vascular syndrome". After the inundation of the noxa, the bradytrophic tissue proves to be an inflammatory niche and thus an ideal antigen reservoir which can sustain the rheumatic process, in particular the humoral and the cellular immune mechanism, for the rest of the organism life. The inflammatory and immune mechanisms, probably continually induced by the persisting antigens, may not be left unconsidered during symptomatic treatment throughout the course of rheumatic diseases.