Anatomy and physiology of white blood cells, also called leukocytes was discussed. We talked about mono nucleated or multinuclear, they are capable of reproduction, even though they are also produced within the bone marrow of the long bones. Viewing a photograph of the blood showed a sample of each type of leukocyte. Using the coronavirus as a current example, the concentration of specific WBC'S will be increased when infection sets in. The function was determined to destroy invading organisms by phagocytosis, and in so doing, produce immunity to future invasion. The history of vaccination was briefly presented, the word derived from the romance language vaca (vacca) referring to a cow. The initial vaccination was to use cowpox scabs inserted into the nasal passages to confer immunity to smallpox. Leukemia, a hyper WBC condition, was briefly discussed, as well as smallpox vaccination.