The EXCURSUS are explicatory monographs examining in greater detail select topics discussed in the first three volumes of The Natural State of Medical Practice. Volume four consists of thirty-one excursus. As additional excursus are written, they will be a continuation of that explicatory process and will later be added to volume four. Because a particular issue will at times overlap or indirectly affect other issues, there is an unavoidable element of repetition of key findings and conclusions from the original work. The monographs also reference relevant pages from The Natural State of Medical Practice, because it is assumed that most readers of the Excursus will not have read the original volumes. Thus, the references are a convenience for locating the original presentation of an issue.