MINUTE ANATOMY OF THE CAPILLARIES. 



283 



lopods. The dark contour lines often exhibit larger or smaller 

 knot-like swellings. Many of these are composed of less deeply 

 tinted substance, surrounded by the intensely brown cementing 

 material, and perhaps consist of some modification of the latter, 

 which is feebly acted on by nitrate of silver. 



The slighter staining may, however, also depend on dimi- 

 nished thickness of the cement, whilst the deeper tints of 

 other parts may proceed from the presence of particles of 

 albumen, belonging to the original contents of the vessel, being 

 retained in small indentations of the cell membrane, and be- 

 coming of a deep brown colour by the action of the silver. 



That the dark lines winding round the nuclei in the silvered 



Fig. 51. Capillaries of the lungs of the Frog, with irregularly den- 

 tated cells. , vascular meshes. 



wall of the vessel are not due merely to albuminous preci- 

 pitates occurring in the small furrows surrounding the several 

 cells, as Auerbach* appears willing to admit, seems to be suffi- 

 ciently refuted by the reactions of the cement in other mem- 

 branes composed of cells, to which no application of nitrate of 

 silver has- been made. Besides the above-described dark inter- 



* Virchow's Archiv, Band xxxiii., 1865, p. 380. 



