THE LUNG PLAGUE. 67 



than a year has elapsed since they were made, they are already considerably altered, and 

 have long been far inferior in distinctness and beauty to those preserved in balsam. 



My experience at the museum has led me to give preference to the method described 

 over any other which I have tried for the purpose of making sections of pathological tissue. 

 The preparations which result closely resemble in appearance those obtained when success 

 fully-made fresh sections are stained with carmine and mounted in glycerine, after Beale s 

 method, and they not merely present the arrangement of the parts with much less displace 

 ment of the elements, but are better suited for study with high powers, and it is possible 

 to prepare satisfactorily much larger and thinner sections. They possess, moreover, the 

 incontestable advantage of being capable of indefinite preservation, and hence I am able 

 to state that those which have served for the following description can be seen at the 

 museum by any microscopist desirous of studying them. 



To illustrate the descriptions here offered, I have prepared a series of photo-micrographs, 

 representing characteristic portions of certain of the sections. The objects photographed 

 are shown with a magnifying power of four hundred diameters, linear. The objective used 

 was the 4th of William Wales, of Fort Lee, New Jersey, which is specially corrected for 

 photography. No eye-piece was employed. The source of illumination in most cases was 

 the oxycalcium light. The process resorted to has been published in full in my recent 

 reports to the Surgeon General on the electric, magnesium, and calcium lights as sources of 

 illumination in photo-micrography, and need not, therefore, be described in this place.* 



The minute structure of the parts selected for study will now be briefly described in 

 the order already indicated : 



1. The alterations in the parenchyma of the lung will be best understood after a 

 brief sketch of the appearances presented by sections made through normal or nearly nor 

 mal portions. Such sections, prepared as already described, and mounted in balsam, af 

 forded quite satisfactory objects for study. Since the morsels of lung selected were not in 

 flated before immersing them into the alcohol, the air vesicles on the periphery of the pieces, 

 of course, collapsed more or less completely. Those in the central portions, however, re 

 tained their shape to a tolerable extent, and from such portions, therefore, the sections 

 were prepared. The air vesicles, as seen in these sections, were irregularly polygonal, 

 approaching a rounded or oval form, and averaged about -gooth of an inch in their long diam 

 eter. Their walls, when cut transversely in the sections, appeared to be composed largely 

 of capillary blood-vessels, the contours of which could readily be observed. The numerous 

 nuclei of the walls of these capillaries averaged smooth of an inch in long diameter. In 

 places where larger vessels came into view, the elements of their walls could usually be well 

 made out, and were generally surrounded by more or less connective tissue, in which elas 

 tic fibers were often prominent. In all the sections there were numerous air vesicles so 

 divided by the knife that, in certain positions of the fine adjustment of the microscope, 

 a view of the inner surface of one of the walls of the vesicle was obtained. This always 

 presented numerous oval nuclei arranged at regular intervals, and delicate contours could 

 generally be traced between them, which, it seemed to me, could be best interpreted, in 

 many cases, by supposing them to be portions of the boundaries of flat, polygonal, nu 

 cleated cells, corresponding to the epithelium of the air vesicles described by some authors. 

 The appearances might also, perhaps, be interpreted by the supposition that the nuclei 



* See also American Journal of Arts and Sciences, May, 1870, the National Medical Journal, April, 1870, and the 

 London Monthly Microscopical Journal for June and August, 1870. 



