Jeremiah S. Ferguson 65 
of the writer to show that these types exhibit well-defined structural 
peculiarities. 
Observations.—The sinusoids, after the careful description by Minot 
(6), will require but brief mention. These vessels possess the wall of a 
capillary and the lumen of a venule. A number of such vessels may be 
seen in Fig. 1, in the central portion of the medulla, on either side of the 
group of central veins. Their wall consists of nucleated endothelial 
plates which rest directly upon the parenchymal cells. Their lumen is 
several times the diameter of the- medullary capillaries. They are dis- 
‘< co 
ee oe Pees 
*3 
rn 
* Lon 
bs. - * d 
‘~ Ge aa = 
Fic. 1. A group of vessels from the central portion of the medulla of the 
human suprarenal gland. a, sinusoids; b, small central veins. Fixation, 5 
per cent formalin; stain, Mayer’s hematein; thickness, 8” ; photomicrograph, 
x 100. 
tinguished from the small central veins by the absence of connective tissue 
from the wall of the sinusoids. 
The small central veins are of the type shown in Fig. 1. The wall of 
these vessels consists of two coats, endothelial and connective tissue. The 
latter is always relatively thin, though the vessels possess a very consider- 
able lumen. Venules of this type of structure, Fig. 1, collect the blood 
from the sinusoids of the medulla. Frequently, however, the sinusoids 
open directly into the small central veins and venules, the connective 
tissue of the venous wall being occasionally continued for a very short 
distance upon the endothelium of the sinusoid. 
5 
