388 
DIGESTIVE SYSTEM OF THE HORSE 
latinus) is a small tube of mucous membrane which extends very obliquely through 
the palatine fissure. 
tissue of the palate. 
Its ventral or palatine end is blind and hes in the submucous 
The dorsal or nasal end communicates with the nasal cavity 
(in common with the vomero-nasal organ) by a slit-like opening in the anterior 
part of the ventral nasal meatus. 
Vessels and Nerves.—The blood-supply is derived chiefly from the palatine 
M. 
i's) 
M. 
ccs) 
Fie. 329.—Harp Pauate anp ApJACENT Part oF Sorr 
Patate or Horse. 
1, Raphé of palate; 2, ridges of palate; 3, soft palate; 
I. 1, I. 2, first and second incisor; Dz. 3, deciduous third 
incisor; P. 1-4, premolars; M. 1-3, molars. 
arteries and the veins go to the vena re- 
flexa. The nerves come from the tri- 
geminus. 
The soft palate (Palatum molle) 
is a musculo-membranous — curtain 
which separates the cavity of the 
mouth from that of the pharynx, except 
during swallowing. It slopes down- 
ward and backward from its Junction 
with the hard palate. The oral surface 
faces ventrally and somewhat forward, 
and is covered with a mucous mem- 
brane continuous with that of the hard 
palate. It presents a rounded, median | 
ridge, flanked usually by a sagittal fold 
on either side. Numerous small ducts 
of the palatine glands open on this sur- 
face. On each side a short, thick fold 
passes to the lateral border of the 
tongue; this is the anterior pillar of | 
the soft palate (Arcus glossopalatinus). 
The pharyngeal surface faces dorsally 
and _a little backward and is covered by 
& mucous membrane continuous with | 
that of the nasal cavity. The free bor- | 
der (Arcus palatinus) is concave and | 
thin; it is in contact (except during deg- | 
lutition) with the epiglottis. It is con- 
tinued by a fold of the mucous mem- 
brane, which passes on each side along 
the lower part of the lateral wall of the 
pharynx and unites with the opposite 
fold over the beginning of the cesopha- 
gus; this fold is termed the posterior 
pillar of the soft palate (Arcus pharyn- 
gopalatinus). The space between the 
diverging anterior and posterior pillars 
(Sinus tonsillaris) is occupied by the 
tonsil (Tonsilla palatina). In the horse, 
however, there is not a compact tonsil, 
as in man, dog, ete., but a series of 
masses of lymphoid tissue and mucous 
glands which extend backward from 
} 
a 
the root of the tongue on either side a distance of about four inches (ca. 10 em.). 
These cause elevations of the surface, on which there are depressions (erypts) in) 
which the gland ducts open. 
The soft palate is greatly developed in equids, its 
average length, measured medially, being about six inches (15 em.). 
Its length and 
contact with the epiglottis may account for the fact that in these animals mouth- ' 
| 
I 
| 
