This monograph is a review and summary of the essential data published in this field. After a brief preface and an introduction, the reviewed material is presented in seven chapters on historic notes and nomenclature, morphology, development, tissue culture, metaplasia, functions, and pathology. The eighth chapter presents a summary and conclusions of the preceding seven. The bibliography lists 359 references. The subject is adequately reviewed and presented. Tissue morphologists interested in endothelium should find this monograph useful.