THE STRUCTURE OF THE LUNG. 



W. S. MILLER. 



The difficulty in unraveling the various subdivisions of the 

 bronchus of higher animals has made it impossible for us to 

 gain a clear idea of the structure of the lung tissue. From a 

 comparative standpoint it has also been impossible to gain 

 light regarding the structure of the mammalian lung, mainly 

 on account of the many variations in the different groups of 

 animals. With these facts in view, I have attempted to re- 

 work the whole subject in question, guided by Dr. Mall and 

 aided by a Fellowship granted by Clark University. I am 

 also under obligations to Dr. Baur for most of the specimens 

 of reptilian lungs. 



Microscopic anatomy has told us that organs are built up of 

 like component parts, and that when the structure of one of 

 these parts is known, the structure of the whole organ is 

 clear. Yet it is necessary to homologize these parts in different 

 animals, and this has been one of my problems. In order to 

 do this we naturally inquire into the evolution as well as into 

 the development of the different lungs. When studied from 

 these standpoints, the structure of the lungs becomes quite a 

 simple affair, provided we employ methods to unravel the more 

 complex lungs. This is made possible by the employment of the 

 more recent methods of reconstruction, which were introduced 

 by His, by Born and many others in embryology, and by Mall,^ 

 Spalteholtz ^ and myself ^ in histology. 



The following methods were found to be of greatest value : 



1. Injecting the lung with air or illuminating gas and then 

 allowing it to dry. 



2. Corrosion preparation in wax or in Wood's metal. 



1 Mall, Blut- u. Lymphwege, etc., Abhandl. d. k. sdch. Gesellschaft d. Wiss., 

 Bd. XIV, 1887, and The Blood-vessels of the Stomach, Joktis Hopkins Hospital 

 Reports, Vol. I. 



2 Spalteholtz, His's Arckiv, 1892. 



3 Miller, Anatom. Anz., 1892. 



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