346 
THE MUCOUS MEMBRANE OP THE INTESTINE. 
2. Brunner's glands—follicles visible to the naked eye, distributed 
singly in the membrane, and most numerous in the upper part of the 
small intestines. 
Very different structures have been confounded under the name of 
hollow viscus, it would present no very exaggerated representation of what I 
(says Dr. Horner) have denominated the superficial vefious layer of the alimentary 
canal, it being also admitted that within the circuit of every anastomosis a follicle 
was formed. Viewed in the preparations of the mucous membrane of the small 
and large intestines which I have, these follicles appear like puncta lachrymalia 
disseminated by thousands over every square inch, and existing so invariably 
upon every part, that as I have stated, the smallest calculation of their numbers 
puts them at from forty to fifty millions.” 
The meshes of the first or superficial venous intertexture are exceedingly minute 
and vary in a characteristic manner in the stomach, small intestines and colon. 
“Nothing short of an entirely successful injection will exhibit this venous anasto¬ 
mosis, as described; and it may be seen either by injecting a vein, or an artery, 
provided the injection passes from the artery into the veins; but the latter process 
is the least desirable, because we lose the benefit of a distinction of colour between 
the two sets of vessels.” 
Doctor Horner has demonstrated the existence of an epidermis in the alimentary 
canal, from the cardiac orifice of the stomach to near the anus, by the following 
process:—“Tear off the peritoneal coat—invert the part and inflate it to an emphy¬ 
sematous condition, the epidermis will then be raised as a very thin pellicle, and 
may be dried in that state; but as this pellicle retains the air, we hence infer that 
it lines the follicles, and is uninterrupted by any perforations. This epidermis, if 
the part be previously injected perfectly, shows dots of injecting matter, but no 
arborescence if it be inflated up from the veins. In so doing the villi disappear, are 
in fact unfolded. 
“The villi cannot be seen to any advantage except they be erected by an injec¬ 
tion, in which case those of the upper part of the small intestines are found to run 
into each other very much like the convolutions of the cerebrum, and to press upon 
each other’s sides in the same way. Some of them, however, are merely semi¬ 
oval plates, the transverse diameter of which exceeds the length. At the lower 
end of the small intestine they become simply conical projections, somewhat curved, 
with the edges bent in, and they retain this mechanism until they entirely disap¬ 
pear near the ileo-coecal valve. In the whole length of intestine there is, however, 
every variety of shape, from oblong curved and serpentine ridges, to the flattened 
cone standing on its base; the first condition changing gradually to the last in the 
descent of the bowel. Conformably to this definition of villi, none exist either 
in the stomach or colon, for there we have only the venous mesh. The villi of the 
jejunum are about the thirtieth of an inch high, and those of the ileum about one- 
sixtieth.” 
Doctor Horner believes that in epidemic cholera the epidermic and venous lining 
of the alimentary canal is exfoliated, whereby the extremities of the venous system 
are denuded and left patulous. This pathological view corresponds with the physio¬ 
logical one referred to in the text, by which the cylinder epithelium covering the 
follicles is separated and becomes mixed with the secretion of these latter during 
digestion. It is only at this time that the follicles are believed to be open. 
In the stomach, according to Dr. Horner, the follicles vary very mnch in size, 
and there is an arrangement whereby many of the smaller ones are seen to open 
into the larger; on an average about two hundred and twenty-five are found upon 
every eighth of an inch square, which would give of course to an inch square 
sixty-four times that amount, or fourteen thousand four hundred follicles, and con¬ 
ceding the whole stomach to present an area of ninety inches, which is probably 
below the mark when this organ is moderately distended, as exhibited in the pre¬ 
paration upon which this calculation is founded, the entire number of follicles is 
one million two hundred and ninety-six thousand. 
Touching the size of the follicles, we learn that “ in the stomach, the largest of 
these follicles is about J^th of an inch in diameter, and the smallest about 5^0th.