A review of the publications, dealing with the morphology of the cartilages of the tracheo-bronchial tree, shows how scarce they are and how fragmentary the contributions based on research. Isolated parts only of the bronchial tree have been investigated, mostly in single specimens or small series. Anatomical textbooks merely state that the trachea and main bronchi are supported by rings and the more distal branches by irregular, circumferentially placed plates which become smaller towards the periphery, until they disappear in the bronchioli. It is at once obvious that this old-time view is not only superficial, but it leaves one completely ignorant about the site where rings cease and plates begin. No information is available about the arrangement of cartilages around the bifurcations of the main bronchi and contradictory descriptions are given about the cartilaginous architecture of the lobar bronchi. A more searching study reveals that cartilages are hardly mentioned in the huge amount of literature on bronchial anatomy which has accumulated since 1880. It is therefore not exagerated to say that the study of this subject has been grossly neglected.

Inhalt
I. Introduction.- II. Historical Review.- A. From Cl. Galenus to Chr. Aeby (1880).- B. From Chr. Aeby (1880).- III. Method and Material.- A. Method.- B. Material.- IV. The Adult Human Bronchial Tree.- A. General Appearance.- B. Terminology.- V. The lower Part of the Trachea.- A. Polymorphism of Rings.- B. Method of counting Rings.- VI. The Tracheal Bifurcation.- A. Own Criteria.- B. Description and Classification.- C. Amount of Cartilage in the Carina.- D. Conclusion.- VII. The Main Bronchi.- A. The Right Main Bronchus.- B. The Left Main Bronchus.- C. Comparison between the Two Main Bronchi.- VIII. The Lobar Bronchi.- A. The Right Upper Lobe Bronchus.- B. The Left Upper Lobe Bronchus.- C. The Middle Lobe Bronchus.- D. The Right Lower Lobe Bronchus.- E. The Left Lower Lobe Bronchus.- F. The Five Lobar Bronchi.- IX. The Pulmonary Hilum.- 1. Rings and Plates.- 2. Where Rings and Plates were found.- 3. Extra- and Intrapulmonary Airways.- 4. The Extrapulmonary Airways.- 5. The Intrapulmonary Airways.- 6. Cartilages Outside and Inside the Lungs.- 7. Conclusions.- X. Foetal Studies.- 1. Embryology.- 2. Histogenesis of Cartilage.- 3. Own Investigations.- 4. Summary and Conclusions.- XI. Age and Sex.- XII. Animal Studies.- 1. Amphibia.- 2. Reptilia.- 3. Aves.- 4. Mammalia.- 5. Summary and Conclusions.- XIII. Morphogenesis.- XIV. Summary.- Acknowledgement.- References.