The demarcation shaft (torus de marcationis, lat.) is an essential component of the immune system, designed to protect the body from external infections and foreign microorganisms. It also plays a key role in maintaining homeostasis (stable balance of the body's internal environment) and preventing the development of autoimmune diseases. The demarcation wall exists in all organisms, but its biological significance is especially important for mammals such as humans and many other animal species. Unlike many other protective mechanisms, the demarcation shaft works independently of the will of a person, and therefore does not require effort to maintain it. Moreover, it is precisely this feature of the demarcation wall that makes it an effective tool of natural immunity, based on the simple principles of “friend-foe” interaction. The human or animal body has a natural reaction to foreign agents called pathogens and creates a protective shell around them. This process occurs regardless of a person’s desire and is called natural immunity. The importance of the demarcation shaft increases during the period of growth, and determines the speed with which the body is able to overcome a foreign agent. A high concentration of demarcation shafts is expressed in high activity of the immune system and the ability to quickly respond to infection. A lack of demarcation shaft can manifest itself in the form of a decrease in the body’s overall defense and a slow response to infection, which significantly increases the likelihood of various diseases.