THE LUNG TLAGUE. 71 



it is in many places, to distinguish the cell forms in which they lie, these are seen to have 

 the character of young connective tissue cells. If, indeed, they are white blood corpus 

 cles, they have then already been transformed to the similitude of the elements charac 

 teristic of the tissue in which they have imbedded themselves, and it appears to me that 

 in the present state of our knowledge we are not yet justified in assuming such a trans 

 formation to be more than a bare possibility. In his criticism of the observations of His 

 on the inflamed cornea, Cohnheim has, as I think, correctly attempted to show that the 

 rows of cells supposed by that author to have proceeded from the proliferation of the cor 

 nea corpuscles are in fact rows of white corpuscles crowded into the channels which 

 normally exist in the corneal tissue, and explains that His was misled by the transforma 

 tions effected in the corpuscles by the reagents he employed. This criticism, however, 

 will not apply with any force to the sections under consideration, for these were all pre 

 pared in precisely the same manner, and those of the lung tissue and of the lymph masses 

 present the pus corpuscles in some places almost quite unaltered, in all readily recogniz 

 able in spite of any transformation they may have undergone, while the new cells, crowded 

 into the connective tissue, have the characters which I have described. 



I invite attention to this subject the more particularly because my study of the essays 

 of Cohnheim lead me to regard his opinion with very great respect. His generalizations 

 and theories are deduced from new observations made by himself and others, very many 

 of which have been confirmed by several careful histologists. A number of them have 

 been satisfactorily repeated under my direction at the Army Medical Museum with similar 

 results. Among these I may particularly specify the new developments with regard to the 

 structure of the blood-vessels resulting from the use of a solution of nitrate of silver as 

 an injecting and staining fluid ; the wandering of the white corpuscles through the vas 

 cular walls in the mesentery of wourarized frogs, when that membrane is inflamed by 

 drawing out a knuckle of intestine through an opening in the abdominal parietes; the new 

 observations on the structure of the cornea, particularly those resulting from its treatment 

 with nitrate of silver, chloride of gold, and its examination while fresh in the moist cham 

 ber, and from the study by these processes of the inflamed cornea of the frog. 



The results of the investigations on these subjects, conducted by myself and rny assist 

 ants, have accorded so well with the descriptions of Cohnheim as to incline me to regard 

 with much favor those of his statements which I have not yet had an opportunity of sub 

 mitting to investigation, but I am not prepared to accept without reserve the ingenious 

 argument by which he attempts to generalize from the facts acquired to the complete 

 interpretation of the process of inflammation, and am of the opinion that much yet remains 

 to be done before we shall be prepared to define with precision the part taken by the 

 migration of the white corpuscles in the inflammatory process. 



In conclusion, I may remark that the future success of investigations into the patho 

 logical histology of the disease under consideration must depend to a great extent upon 

 the progress made in our knowledge of the minute anatomy of the healthy lung. At the 

 present time the methods of research at our disposal are not such as to overcome com 

 pletely the difficulties offered by the complex structure of this organ. Observers have not 

 even agreed as to the solution of such apparently simple questions as the existence of an 

 epithelium in the air vesicles. More intricate problems, such as the minute relations of 

 the lymphatics, for example, lie still in utter darkness. Future success in these imper- 



