381 



in 1870.^ Both these authors have failed to see the Avhite 

 blood corpuscles pass through the coats of the small vessels 

 in the manner desciibed by (Johnheim^ and deny the existence 

 of stomata, between the cells of the vascular epithelium, large 

 enough to permit such a Avandering to occur. 



After I had perused Cohnheim's paper I procured a 

 number of frogs, and having on hand a small quantity 

 of Wourara, the gift of my friend Dr. S. Weir Mitchell 

 of Philadelphia, I carefully repeated many of the expe- 

 riments described. I received the mipression from what 

 I saw that Cohnheim was a most conscientious observer, 

 who had described as faithfully as possible the impressions 

 made upon him. Certainly the results I obtained, by fol- 

 lowing his methods of producing inflammation in the cornea 

 and mesentery of frogs, could be described in his very 

 language without drawing upon the imagination. Never- 

 theless my other duties did not leave me sufficient time for 

 an exhaustive research in this difficult domain, and it is far 

 from my present purpose to enter into a critical discussion of 

 the subject. It is simply my desire to offer a brief descrip- 

 tion, illustrated by Photo-micrographs, of certain preparations 

 in the Microscopical Section of the Museum, which bear 

 upon some of the points involved, and thus to contribute 

 what is in my power towards the important object of arriving 

 at certainty with regard to the facts on which our future 

 theories of inflammation are to rest. 



Most of the ^^reparations here referred to are examples of 

 the results attainable by staining the tissues with a dilute 

 solution of the nitrate of silver. This re-agent has been em- 

 ployed for various histological purposes du-ring the last ten 

 years, and has attracted attention especially in connection 

 with the cornea, the various forms of connective tissue, the 

 ultimate branches of the lymphatics and the boundaries of 

 the cells which constitute epithelial surfaces. General atten- 

 tion was first drawn to its use by Dr. F. von Recklinghausen, 

 of Berlin, in 1860," and further particulars were contributed 

 during 1861, by Prof. His, of Basel,^ who would appear to 

 have already employed the re-agent for several years. In 



attach importance to this paper should read the caustic criticism of Dr. 

 Alexis Sclikiarewski of Moscow. lb., Bd. xlvi, S. IIG. 



' " llecherches Experimeatales sur le passage des Leucocytes a travers 

 les parois vasculaires ;" ' Journal de I'Anatomie et de la Physiologie,' Jan. 

 & Peb., 1870, p. 33. 



2 " Eiue Methode, mikroskopische hohle and solide Gebilde von eiuander 

 zu unterscheiden ;" ' Virchow's Arcliiv,' Bd. xix, S. 451. 



^ " Ueber das Verhalten des Salpetersaureu Silberoxyds zu thierischen 

 Gewebsbestandtheileu;" lb., Bd. xx, S. 207. 



VOL. X. — NEW SER. C C 



