In this paper many of the principal struc­ture of the Moral Lung were studied with the help of Electron Microscopy. Detailed descrip­tion was given of Granular Pneumocytes, Membranous Pneumocytes, Macrophages, and Alveolar Capillaries. A discussion followed on the form and function of Granular Pneumo­cytes. 

Acknowledgements 
I am grateful to the Reza Shah Pahlavi Foundation for its generous support of this study, and to Dr. S. C. McDonald for his advice in this paper.