284 THE BLOODVESSELS, BY C. J. EBERTH. 



vening portions, clear areas of various size are also observable, 

 interposed between the plexuses of lines. The margins of 

 these are, for the most part, similarly dentated to those of the 

 adjoining cells, but they are always of smaller size, and destitute 

 of nuclei. 



These appearances are not so frequently met with in the 

 capillaries of mammals, but are common in the large arteries 

 and veins, and also in the vessels of lower animals ; as, for 

 example, in the Cephalopods. Many of these non-nucleated 

 areas (intercalated areas, as Auerbach calls them), may fairly 

 be regarded as portions of the vascular cells which have been 

 pinched off. 



Small, irregularly shaped, dark, sharply defined spaces may, 

 after treatment with nitrate of silver, be met with within as 

 well as between the cells. 



The number of the dark and clear intermediate areas varies 

 much in different individuals, and more in the arteries and 

 veins than in the capillaries. It has not been clearly proved that 

 they are actually spaces in the wall (Stomata of Cohnheim). 

 To enable us to understand the passage of blood corpuscles 

 through the vascular walls, it is not requisite that coarse spaces 

 or openings should exist, provided we may regard the vessel 

 as composed, not of a stiff, but of a soft material, forming an 

 elastic and permeable membrane. If the openings were really 

 coarse, colouring particles of large size would pass through the 

 vascular wall in various regions. But this never occurs. We 

 do indeed see that fine colouring particles* escape through the 

 vascular wall, but this does not occur easily with those possess- 

 ing the diameter of the colourless blood corpuscles. These, on 

 the other hand, by reason of their 'softness and elasticity, 

 accommodate themselves to the fine invisible pores of the 

 vascular membrane, and having traversed these, regain their 

 original form. 



Their escape must not, however, be regarded as a simply 

 passive process, like the filtration of a colloid substance, to 

 which it was likened in the first instance by Hering ;f for it 



* W. Reitz, Sitzungsberichte der Wiener Akademie, Bandlvii., 1868. 

 t Wiener Sitzungsberichte, Band Ivii., 1868. 



