STRUCTURE OF THE MUCOUS MEMBRANE. 
411 
perfectly flat, or slightly raised, according to the degree of 
arrest of development ; an oval zone of these openings, such 
as I am now describing, measured ^ of an inch in length by 
y l o of an inch in breadth. The central area differs, then, in 
its degree of conical prominence, such prominence being 
sometimes wholly wanting; but whether such prominence 
exist or not, there is always the same arrangement of vessels 
as in a perfect villus, a central artery and vein, and a delicate 
capillary plexus, finer considerably than that of the villus, 
radiating from the centre to the circumference, and there 
being continuous with the intervillous plexus, the zone of 
crypts or simple follicles occupying the larger meshes of the 
intervillous plexus around the base of the aborted villus. 
The structure which I am now describing, that is to say, a 
slightly convex disc, surrounded by a zone of simple follicles, 
has heretofore been considered as a gland of the small intestine, 
a sacculated follicle or gland without excretory aperture, as in 
fact the glandula solitaria of the small intestine. After close 
examination, I can find nothing to warrant such a conclusion. 
The Lamellated Mucous Membrane I found upon and between 
the valvulae conniventes of the jejunum ; it was composed of 
lamellae of an inch in breadth (divested of epithelium) 
and variously convoluted and intertwined. The lamellae were 
of considerable length, and about equal in depth to the villi 
of an inch), but so closely packed together that no ground 
surface was visible between them. I was therefore unable to 
determine the presence or absence of simple follicles. 
A portion of* the mucous membrane of the jejunum lying between the 
valvulae conniventes, magnified nineteen times, and showing the lamellated 
and convoluted form of villi ; the breadth of the lamelke is 550 of an inch. 
GLANDS OF THE ALIMENTARY MUCOUS MEMBRANE. 
The glands of the mucous membrafae of the alimentary 
Fig. 4. 
