| | STRUCTURE OF THE INTESTINES. 1015 
(4 inches from the pylorus) they have become distinct and prominent. In the 
rest of the duodenum, and in the upper half of the jejunum, they are highly 
developed, being large, broad, and closely set. In the lower half of the jejunum 
they become oradually smaller and fewer. Passing down into the ileum, they 
become still smaller and more irregular, and, as a rule, they practically cease a little 
below the middle of the ileum. 
The mucous membrane covering the folds possesses villi, solitary glands, and 
Lieberkiihn’s glands, like the mucous membrane of the general surface between the 
valves. 
Often patches of valvulee conniventes, much reduced in size, can be traced to within a short 
distance of the ileo-ceecal valve. According to Sappey, Luschka, and others, they usually reach to 
within two or three feet of the end of the ileum. 
They are said to be absent in mammals, with the exception of man and the ornithorhynchus. 
Solitary Glands (noduli lymphatic solitari1).—These are minute nodules of lym- 
phoid tissue, opaque and of a whitish colour, found projecting on the surface of the 
mucous membrane throughout the whole length of both the small and large intestines. 
Isolated lymphoid cells are found in abundance scattered through the connee- 
tive tissue layer of the intestinal mucous membrane generally; in places these 
cells are gathered together to form little nodules, supported by a framework of reti- 
form tissue, and surrounded by a lymphatic space which communicates below with 
the lymphatics of the submucosa. Such a collection of lymphoid cells constitutes 
a solitary gland. They are usually of a rounded or oval shape (Fig. 684), the 
wide end re esting in the submucosa, the nodule itself 
piercing the muscularis mucose, and the narrow end 
projecting slightly above the surface of the mucous 
membrane. In size pean rary from ;gth to 3th of an 
inch (6 to 3°0 mi.), but their average bulk is about 
that of a small grain of sago, to which they bear 
some resemblance. 
As already mentioned, they are present throughout 
the small and large intestines, beimg particularly 
abundant in the vermiform appendix and cecum. 
In the small intestine they are found on the 
valvulee conniventes, as well as upon the general 
surface of the mucous membrane between them. 
Peyer's Patches, or Agminated Glands (noduli lym- 
phatic1 aggregati, tonsille intestinales).— A Peyer's 
patch consists of a large number of lymphoid nodules 
erouped closely together so as to form a shghtly ele- 
vated area, usually ‘of an oblong form, on the surface of 
the mucous membrane (Fig. 686). In length they vary 
from half an inch (12 mm.) or less to three or four 
inches (100 mim.), and in width they commonly measure 
from a third to half an inch (8 to 12 mm.). Their 
number is variable, but in the average condition about 
30 or 40 are found. They are best “marked in young 
subjects, where they form considerable elevations 
above the general surface, and may be as many as 45 /!s_.86.—Payvers Fatcu AnD 
‘ 5 SOLITARY GLANDS, from intestine 
in number. After middle life they atrophy, and Gilehildiiiwoiaenrscoldbtnnturel 
Two solitary glands Peyer's patch 
\ 
Solitary gland Intermediate form 
in old age, although usually to be found, they are size). 
indistinct, occasionally being marked by little more Near the lower border are seen a 
than a dark discoloration of the mucous membrane. few small patches made up of 
They are invariably situated along the free surface TRE LMR EEL 
of the intestine opposite the line of mesenteric form.” 
attachment, with their long axis corresponding to 
that of the bowel. Consequently, in order to display them, the tube must be slit 
up along its attached or mesenteric border. 
Peyer’s patches are entirely confined to the small intestine, being largest and 
