474 
DE. HEEBEET WATNEY ON THE MINUTE 
The Character of the Membrana Propria. 
The membrana propria of the surface of the villus-like processes is formed of endo- 
thelial cells. In section they are seen as oval or rounded cells ; on surface view they 
appear as polygonal plates. I have never been able to separate the membrana from the 
rest of the mucosa. The membrana of the ducts, when seen from the surface and com- 
pletely isolated from the surrounding structures, is exactly like that of Lieberkuhn’s 
crypts, namely, a structureless membrane, with oval nuclei imbedded in it at intervals. 
The Muscle-endings in the Plicae Villosce and the Perivascular Spaces. 
In specimens hardened in chromic acid, the muscles arising from the muscularis 
mucosas are seen passing up between the glands and entering the plicae villosae. If these 
villus-like processes of the mucous membrane are very narrow, two bundles of muscular 
fibres will be seen, one on each side of a central clear space, and in contiguity with it. 
The muscle bands running up to the tops of the plicae villosae and spreading out, end 
by being attached to the membrana ; some of the fibres may cross above the clear space, 
or pass to the side of it to be attached to the membrana of the other side of the villus- 
like process ; the mode of their attachment is exactly like that which has been already 
described in the colon of the rabbit (compare fig. 36, Plate 43, with fig. 10, Plate 39). 
The clear space enclosed by the muscle bands is seen to contain a blood-vessel, and is 
formed of endothelial plates. 
The blood-vessels in the narrower plicae villosae run vertically, but, at times, they bend 
horizontally. If in the section they bend towards the observer, the blood-vessel is seen 
to be surrounded by a clear ring (perivascular space). In the broad villus-like processes 
where the blood-vessels run in a direction parallel with the surface, the upper wall of 
the perivascular space is formed by the membrana propria : thus we have here an arrange- 
ment somewhat similar to that described by Boll (71) and Leydig (69) in the salivary 
glands, and by Ludwig and Tomsa (101) in the testicle, namely, a blood-vessel enclosed in 
a perivascular space, one wall of which is formed by the membrana propria, the mem- 
brane supporting a secreting epithelium. 
These perivascular spaces are probably the same as those lymph-vessels of the stomach 
which have been injected by Professor Loven (96) by the method of puncture ( loc . cit. 
figs. iv. & x.). 
In the broad villi great numbers of muscle-fibres are always present ; and fig. 36 
shows how they form membranous layers, which lie in contiguity with the endothelial 
plates of the perivascular membrane. This arrangement reminds us at once of the 
relation of the muscle-fibres to the walls of the chyle-vessels of the villi in the monkey. 
The action of the muscles on the plicae villosae will be twofold : when they contract they 
will shorten the villi, and further they will cause them to become smaller in their 
transverse diameter. This follows from the disposition of the bands of muscle : they 
expand in a fan-like manner in the upper part of the villi, some of the fibres crossing 
over to be attached to the other side. 
