STRUCTURE OF THE MUCOUS MEMBRANE. 
409 
term in this sense being synonymous with pilus (a hair), so 
that we might use indiscriminately the term villous or pilous. 
Such appears to me to be the anatomical signification of 
the terms “ villous” and “villus.” We first apply the term 
as indicative of the vellus or fleece of the mucous membrane, 
“ vellus” being derived from “ velare,” to clothe ; and, 
secondly, we analyse the construction of the vellus, and find 
it to be composed of minute pili, to which we give the name 
villi, and from the latter we deduce the adjective villous. In 
this sense, therefore, villous not only applies to a fleecy nap 
developed on a surface, but also to the particular composition 
of that nap of pili or villi. 
I am thus particular in my endeavours to fix the exact 
meaning of the term “villous” and “ villi,” because a large 
portion of the mucous membrane of the small intestine is 
constructed on a different principle to this, one in which 
there are no villi, but in their place the surface of the mem- 
brane is raised into laminated or lamellated folds, these folds 
or plaits having a gyrated or convoluted arrangement. 
Hence, 'the villous, or rather vellous, mucous membrane 
admits of a division into that which is composed of villi, the 
true villous, or simply the villous and the lamellated. 
Fig. 3. 
A portion of the mucous membrane, magnified nineteen times, showing 
conical villi. In the hollows between the villi are seen the apertures of 
simple follicles ( b ) ; and near the bottom of the figure is a zone of follicles 
(a), surrounding what has been described as a solitary gland. These villi 
measured ^ of an iuch in length, by ^ in breadth at the base, and from 
lb to iso of an inch near the summit. 
In the villous mucous membrane the villi are, for the most 
part, conical in shape with obtusely rounded points, and 
