The article discusses the theory of immunity, focusing on two main theories: METCHINIKOFF's phagocytosis theory and HANKIN's serum theory. METCHINIKOFF's theory attributes immunity to the action of ameboid cells that engulf and digest bacteria, while HANKIN's theory suggests that immunity is due to substances formed by the metabolism of animals that can destroy microbes or their pathogenic products. The article highlights the importance of considering both microbial and cellular products in the immune response. It also mentions the research of BEHRING and KITASATO on tetanus and diphtheria, where the struggle is between poisonous and preservative proteins. The article concludes by emphasizing the need to understand the morphological, chemical, and dynamic aspects of vital phenomena and processes. The second part of the article discusses the evolution of arthrectomy, the surgical removal of diseased joints. It acknowledges the contributions of SYME, LISTON, FERQUSSON, and BUTCHER in establishing conservative surgery. However, the practice has advanced significantly, with excision being largely replaced by erasion, which leaves the limb and joint in better condition. The article outlines several factors contributing to this advancement, including better understanding of joint diseases, Koch's discovery of the tubercle bacillus, antiseptic surgery, and the invention of the sharp spoon by VOLKMANN. The leading principles of dealing with diseased joints include removing only pathological material, conducting procedures under strict antiseptic precautions, and avoiding tension. Early operation is recommended to prevent the need for severe later procedures, and constitutional treatment is used as an adjuvant.The article discusses the theory of immunity, focusing on two main theories: METCHINIKOFF's phagocytosis theory and HANKIN's serum theory. METCHINIKOFF's theory attributes immunity to the action of ameboid cells that engulf and digest bacteria, while HANKIN's theory suggests that immunity is due to substances formed by the metabolism of animals that can destroy microbes or their pathogenic products. The article highlights the importance of considering both microbial and cellular products in the immune response. It also mentions the research of BEHRING and KITASATO on tetanus and diphtheria, where the struggle is between poisonous and preservative proteins. The article concludes by emphasizing the need to understand the morphological, chemical, and dynamic aspects of vital phenomena and processes. The second part of the article discusses the evolution of arthrectomy, the surgical removal of diseased joints. It acknowledges the contributions of SYME, LISTON, FERQUSSON, and BUTCHER in establishing conservative surgery. However, the practice has advanced significantly, with excision being largely replaced by erasion, which leaves the limb and joint in better condition. The article outlines several factors contributing to this advancement, including better understanding of joint diseases, Koch's discovery of the tubercle bacillus, antiseptic surgery, and the invention of the sharp spoon by VOLKMANN. The leading principles of dealing with diseased joints include removing only pathological material, conducting procedures under strict antiseptic precautions, and avoiding tension. Early operation is recommended to prevent the need for severe later procedures, and constitutional treatment is used as an adjuvant.