382 



1862 Von Recklinghausen published his work on the lym- 

 phatics,^ which contains a detailed account of many elaborate 

 exj)eriments with regard to the action of silver solutions on 

 the tissues, and in 1863 Dr. Ernst Oedmanson, of Stockholm,^ 

 gave a description of their behaviour when applied to epithe- 

 lial surfaces, and described and figured the so-called stomata 

 which play so important a part in the theory of Cohnheim. 

 During 1865 and 1866 the epithelium of the capillary blood- 

 vessels, as shoAvn by silver, was described by several observers, 

 among whom Dr. N. Chrzonszczewsky, of Charkow/ may 

 be particularly mentioned. 



The perusal of these papers led me to make a number of 

 experiments myself, and to have others made by my assistants 

 at the Museum, the results of which are now to be described. 



If a dilute solution of nitrate of silver is brushed over a 

 clean epithelial surface taken from a recently killed animal, 

 and the tissue after washing with distilled water is exposed 

 for a short time to the action of sunlight, it will be found on 

 microscopical examination that a brownish-black precipitate 

 of silver has been produced at the boundaries of the epithelial 

 cells, while the cells themselves are comparatively but little 

 stained, or if the manipulation has been carefully conducted, 

 are not stained at all. For this purpose I have most fre- 

 quently employed, at the Museum, a solution made by dis- 

 solving one part of crystallized nitrate of silver in four 

 hundred parts of distilled water, but considerable variation 

 on either side of this strength does not much modify the 

 result, provided the solution is well Avashed off before the 

 tissue is exposed to the light. 



If the same solution is injected into the blood-vessels, the 

 lining epithelium is handsomely mapped out in all those 

 membranous and superficial parts in which a ready exposure 

 to the action of light is practicable, and although in the 

 parenchymatous organs, such as the liver, the spleen, the 



' 'Die Lymphgefasse und ihre Beziehung zurn Bindegewebe ;' Berlin, 

 1862. 



2 " Beitrag zur Lehre von dem Epitliel ;" ' Vircliow's Arcbiv,' Bd. xxviii, 

 S. 361. 



^ " Ueber die feinere Structur der Blutcapillaren ;" ib., Bd. xxxv, S. 169. 

 C. J. Eberth in his article on the blood vessels in Stricki^r's Handbook 

 ('Handbuch der Lelire von den Geweben,' &c. Leipsie, 1869. 11. Lief: 

 S. 202) enumerates the following microscopists as having described the epi- 

 thelium of the capillaries prior to Chrzonszczewsky. Hoi/er. ' Archiv. fiir 

 Anatomic,' Jan. 18, 1865. Auerhach. 'Breslauer Zeitung,' Feb. 17, 1865. 

 Eberth. ' Sitzungsbcrichte der pliybikal. med. Geseliscliaft zii Wiirzburg,' 

 Feb. IS, 1865. ' Medicinisches Centralblatt,' No. 13, 1865. ' Wiirzburger 

 Naturwissenschaftliche Zeitschrift;' Bd. vi, 1866. Aeby. Medicinisches 

 Ceutralblatt. No. 14, 1865. 



