The class started with a review and expansion on the antigen-antibody reaction, allergens, and anaphylactic reaction. The factors which would affect exogenous chemical responses in the body were outlined and discussed. They included the process of absorption, the routes of administration (oral iv, transdermal, etc), the physical form of the chemical (liquid, tablet, powder, etc). The organ of absorption,the small intestine along with the villi were examined. Distribution and metabolism will be next.