1044 _ THE DIGESTIVE SYSTEM. ~— 
Columns of Morgagni (column recti Morgagni).—The mucous membrane of 
the anal canal presents, in its upper, and part of its middle thirds, a number (5 to 
10) of permanent vertical folds, separated by grooves, and known as the columns 
of Morgagni (Fig. 705). 
; They are usually 4 to $ 
fq inch (8 to 12 mm.) in 
length, $ to + inch (3 to 
Rugeot 6 mm.) in width, and they 
p-mucous io extend down to within 4 
membrane 
Longitudinal 
fibres of 
rectum or # inch (12 to 7 mm.) of 
12 Col s of 
_Morgagni the anal aperture. They 
Part of are formed by infoldings of 
levator ani» 
the mucous membrane, con- 
taining in their interior 
some unstriped muscle de- 
rived from the muscularis 
mucose, and also, as a rule, 
an artery and a vein. 
é 
Internal 
sphincter 
g 
Anal canal< a : 
ae 
Very often the contained 
vein presents an enlargement, 
or a knob-like tortuous plexus 
be ; _ in the lower part of the 
Showing the columns of Morgagni and the anal valves between their 
lower ends. The columns were more numerous in this specimen column ; below this the plexus 
than usual. is continued down beneath the — 
mucous membrane of the 
lower zone of the anal canal into the anal veins (see page 1045). This portion has 
accordingly been described as the hemorrhoidal zone of the anal canal. Sometimes 
the columns of Morgagni are very indistinct ; occasionally no trace of them can be found, 
although in the foetus (Fig. 706) they are usu: illy well marked. | 
Fic. 705.—TuHeE INTERIOR OF THE ANAL CANAL AND LOWER PART 
oF RECTUM, 
Anal Valves (of Morgaegni).—If a probe be passed downwards along the 
groove which separates two adjacent columns of Morgagni (Fig. 705), its “point | 
will usually catch in a small crescentic fold which joins the lower ends of the two — 
columns. These little folds, which resemble in miniature the segments of the — 
semilunar valves of the heart, are the anal valves. They project inwards and 
upwards, and behind each 
is found a little pocket- 
like sinus (sinus rectalis). 
These valves were first 
described by Morgagni. Re- 
cently the view has been 
advanced by Ball that they 
are the remains of the em- 
bryonic cloacal or anal mem- 
brane; and he explains the 
production of “painful fissure 
of the anus” by the tearing Fic. 706.—Tue ANAL CanaL AND LOWER Part oF RECTUM IN THE 
down of one of them during Fetus. 
defeecation by hardened 
A, aged 4 to 5 months; B, 6 months; and C, 9 months. In each the anal 
masses of fieces. big canal is distinctly marked off from the rectum proper ; the columns of 
The epidermis is con- Morgagni and the rectal valves are distinct. R.V. Rectal valves. 
tinued in a thin and modified 
form from the exterior up along the anal canal as far as the margins of the anal valves; and the 
view is pretty generally held that only this lower portion of the ‘anal passage is formed from the 
proctodieum 1 in the embr yo. The junction of the skin with the mucous membrane is indicated 
by a fine wavy line (“white line” of Hilton—ano-cutaneous line of Hermann) which runs around 
the bowel at the level of the valves. The mucous membrane of the region immediately above 
the anal valves is of a more or less transitional nature ; glands are absent from it, and over the 
columns of Morgagni it is said to be covered with stratified epithelium, the superficial cells of 
which are flattened, whilst in the grooves between the columns the epithelium is columnar. 
In the upper zone of the anal canal the mucous membrane gradually approaches to the rectal 
type, but the Lieberkiihn’s glands and lymphoid nodules are few and scattered. 
Anus or Anal Orifice—At the inferior aperture of the anal canal, the 
