412 STRUCTURE OF THE MUCOUS MEMBRANE. 
canal are usually divided into three groups — tubular, saccular, 
and compound. 
Tubular Glands . — The tubular glands are the simple crypts 
or follicles, mere inflections of the limitary membrane into 
the substance of the corium, terminated in cul-de-sac or in 
small dilatations or loculi. 
The follicles of the stomach, the gastric or pepsiniferous 
follicles, are longer than those of the intestine, and loculated 
at the extremity. They open, as already described, into the 
floor of the alveoli, from six to twelve into each alveolus. 
Their apertures are oval in shape, and, divested of epithelium, 
measure in long diameter T gVo °f an inch. 
The follicles of the small intestine, the crypts or simple 
follicles of Lieberkuhn, are simple caecal pouches, terminating 
in cul-de-sac , without loculated extremities, and shorter than 
the gastric follicles. They are found most abundantly in the 
villous mucous membrane ; namely, in the intervillous spaces, 
where they occur in small clusters — two, three, four, or five ; 
around the bases of the villi, where they form circles or zones; 
around the aborted viilia (the so-called solitary glands), where 
they also form circles or zones ; and in the floor of the alveoli 
of the aggregated glands of Peyer. 
Simple follicles have also been described as entering into 
the structure of the large intestine, the alveoli of the mucous 
membrane have been mistaken for the apertures of glandular 
crypts. The alveoli and the glands which they contain are, 
however, perfectly distinct from the follicles now under con- 
sideration, and different in structure. If simple follicles 
exist at all in the mucous membrane of the large intestine, 
they are most likely to be found at the bottom of the hollow r 
cavities of the solitary glands, where I think I have detected 
them. 
Simple tubular follicles or crypts are, therefore, found in 
three situations; namely, 1, In the stomach, under the name 
of gastric follicles ; 2, In the villous mucous membrane of 
the small intestine; and 3, In the alveoli of Peyer’s glands. 
Their presence in the lamellated mucous membrane of the 
small intestine I hold to be undetermined ; and in the large 
intestine I hold them to be absent with the exception men- 
tioned above. 
Saccular Glands . — The so-called saccular glands, consisting 
of a lentil- shaped sacculus or capsule placed beneath the 
limitary membrane, and having no excretory aperture, I 
believe to have no existence. The recognised instances of 
these glands are the lenticular glands of the stomach, the 
glandulae solitarise of the small intestine, and the glandulae 
