Basic anatomy and histology of the lung. 
All studies of toxic effects must compare normal conditions with those existing after contact with the toxin.  If the effects to be studied involve alterations of gross, microscopic or ultramicroscopic structures, then a knowledge of normality at each of these levels is essential.  This understanding is equally true for every organ of the body from the skin to the bones.  Our interest today is in the pulmonary effects of phosgene; consequently, this discussion of basic morphology will be directed entirely at the lower respiratory tract.  While most of the research to be presented in subsequent papers will relate to experimental studies in animals of various species, all are probably intended to have relevance to human responses to contact with phosgene.  This discussion, therefore, will be concerned with the human lung and with examples of two animal species, rats and dogs.  Since any single author can do relatively little of the vast range of studies necessary to establish normal morphology, this discussion is necessarily derived largely from the literature.  Rather than present copies of illustrations and charts, which would require extensive copyright negotiations, and many of which would lose detail in reproduction, its seems best to refer the reader to the original publications.  Most of these are readily available in medical libraries.