This Chapter is from The Yellow Emperor's Classic of Internal Medicine, specifically Chapter 79, "The Spiritual Pivot – The Discussion of Seasonal Exposures." It explores the relationship between seasonal changes, the body's defensive energy (wei qi), and the susceptibility to illness. The dialogue between the Yellow Emperor and his physicians Qi Bo and the Minor Master examines the mechanisms of disease transmission, emphasizing the role of pore openings, the movement of pathogenic qi through meridians, and the influence of lunar cycles. The text also details how seasonal winds and weather patterns correlate with the prevalence and severity of various illnesses, even predicting mortality rates based on specific wind directions. Finally, it introduces the concepts of "Three Vulnerabilities" and "Three Strengths" to explain individual susceptibility to disease.