08 DEPARTMENT OF AGRICULTURE. 



belonged to the capillaries of the wall in view, and the delicate contours might be referred 

 to the limiting membrane of these vessels, but it seemed to me that neither the relative 

 position of the nuclei, nor the direction of the contours, corresponded so well with this 

 view as with that first mentioned. The nuclei, moreover, were somewhat broader than 

 those of the undoubted capillaries in other portions of the section, though of the same average 

 length. The epithelial cells, if such they were, averaged jsV&th of an inch in long diameter. 



The first of the photo-micrographs appended, represents a portion of one of these 

 sections, (No. 2801, Microscopical Section,) and exhibits the appearance described, as seen 

 with 400 diameters. In arranging the focal adjustment of the microscope so as to bring 

 into view that portion of the wall of the air vesicle which displays the epithelium-like 

 appearance, the rest of the section is necessarily thrown out of focus, and is so represented 

 in the photograph. 



When, now, sections of the diseased portions of the lung were compared with the 

 above, the most noteworthy alteration observed was in the contents of the air vesicles. 

 These, which had been quite empty in the healthy lung, were in the diseased portion 

 found to contain pus corpuscles in variable numbers. All possible transitions could be 

 seen between vesicles containing a few scattered corpuscles and those in which the whole 

 cavity was filled with them. Where the pus corpuscles were not numerous enough to 

 obscure the view, delicate fibrin filaments could generally be made out between them, so 

 that the contents of the air vesicles were, in fact, quite similar in composition to the lymph 

 masses on the surface of the pleura and in the interlobular trabeculae, which will be 

 presently described. The sections containing but a few scattered pus corpuscles were 

 from the reddened and codematous portions of the lung, which, however, still contained 

 enough air to enable them to float on water; those containing numerous pus corpuscles, 

 with fibrin filaments between, were from portions of the lung which had entered, more or 

 less completely, into the stage of red hepatization, while those which were stuffed so full 

 of pus corpuscles that the shape of the air vesicle and its relations to neighboring parts 

 were quite obscured, were from the most completely hepatized portions, or from those 

 which had passed into the condition of gray hepatization. 



With these changes in the contents of the air vesicles of the diseased lung, altera 

 tions undoubtedly occurred in the walls of the air vesicles. In the sections they appeared 

 thicker than normal, they took up carmine more abundantly when stained, and their 

 texture became more and more granular in the more completely hepatized portions of the 

 parenchyma, so that it was difficult to make out their structure and to trace the precise 

 changes which they had undergone. With these changes there was associated a notable 

 diminution in the cohesiveness of the tissue, which became friable and easily torn, as has 

 long been observed in the case of pneumonic lungs in the human subject. I regret greatly 

 that the time at my disposal did not permit more elaborate research with regard to these 

 changes, yet cannot avoid the opinion that the difficulties to be encountered in this 

 direction are so great as materially to diminish the probability that more protracted efforts 

 would have proved fruitful in the present incomplete state of our knowledge of the 

 histology of the lung. I append two photo-micrographs taken from one of these sections, 

 (No. 2808, Microscopical Section,) each magnified 400 diameters. They exhibit partially 

 hepatized portions of the lung in which the air vesicles contain the pus corpuscles and 

 fibrin filaments above described. The second photograph represents a rather more advanced 

 stage than the first. 



