The book "The Action of Medicines in the System, or the Way in which Therapeutic Agents Administered into the Stomach Affect the Animal Organism" by Frederick William Hedland is one of the essential sources for understanding the effects of drugs on the body. In the book, the author explains in detail the mechanism of action of drugs, the study of which allows a better understanding of how therapeutic agents affect the body and cause certain effects. This scientific work has become an important addition to modern medical literature and is an important source of knowledge for doctors and specialists in the field of medicine.