THE PHARYNX—THE (SOPHAGUS—THE STOMACH 497 
maxillary nerve. It has four or five ducts which open near the last upper cheek 
tooth; one of them (Ductus glandule zygomatic major) is almost as large as the 
parotid duct; the others (Ductus glandulxe zygomatic minores) are small. 
THE PHARYNX (Fig. 434) 
The fornix is narrow. The pharyngeal orifices of the auditive or Eustachian 
tubes are small and slit-like; the end of the tube causes a rounded projection of the 
mucous membrane (Torus tubarius). The cesophageal aditus is relatively small 
and is well defined by a transverse fold of the mucous membrane. The muscles 
present no marked differential features, but the hyo-pharyngeus muscle is clearly 
divided into a kerato-pharyngeus and a chondro-pharyngeus. 
THE (ESOPHAGUS 
The cesophagus is relatively wide and dilatable except at its origin, where there 
is a constriction termed the isthmus cesophagi. This initial narrowness of the 
lumen is caused by a prominence of the ventral part of the mucous membrane, 
underlying which is a thick layer of mucous glands (Fig. 490). The cervical part 
is at first median and is dorsal to the trachea, but in the posterior part of the neck 
it lies to the left of the trachea. The thoracic part continues in this position and 
ventral to the left longus colli to the base of the heart; here it inclines medially, 
having the aortic arch on its left, and passes back over the bifurcation of the trachea. 
Continuing backward between the lungs it usually inclines slightly to the left, 
passes through the hiatus cesophageus, and joins the stomach just to the left of the 
median plane and ventral to the eleventh or twelfth thoracie vertebra. The 
muscular tissue is striated and consists mainly of two layers of spiral fibers which 
cross each other; near the cardia, however, the fibers are longitudinal and circular. 
There are tubulo-alveolar glands (Gl. cesophage) in the submucosa throughout. 
THE STOMACH 
The stomach is relatively large. Its capacity in a dog weighing about 40 
pounds is about six to seven pints. 
Colin estimates the average capacity at about 3 liters (ca. 614 pints), with a range between 
0.6 and § liters (ca. 14 to 1714 pints). Neumayer gives the capeaity as 100 to 250 e.c. per kilogram 
of body-weight (ca. 2.7 ounces per pound). The average capacity of the human stomach is esti- 
mated at 1.2 liters (214 pmts)—not much more than a third of that of a dog of medium size. 
When full, it is irregularly piriform. The left or cardiac part (Fundus et corpus 
ventriculi) is large and rounded, while the right or pyloric part (Pars pylorica) is 
small and cylindrical. When empty, or nearly so, the left sac is strongly contracted; 
the pyloric part is much less affected by variations in the amount of ingesta. 
The parietal surface of the full stomach is very extensive, strongly convex, 
and faces partly forward, but largely ventrally and to the left. It is related to the 
liver, the left part of the diaphragm, and the left and ventral abdominal wall as far 
back as a transverse plane through the second or third lumbar vertebra. The 
visceral surface is much less extensive and is considerably flattened; it faces chiefly 
dorsally and to the right, and is related to the intestine, pancreas, and left kidney. 
The upper part of the lesser curvature is nearly straight and vertical, but the 
lower part forms a deep, narrow angle (Incisura angularis), due to the fact that the 
pyloric part is directed sharply forward and upward. The greater curvature is 
nearly four times as long as the lesser curvature. In the full stomach it extends 
considerably behind the left costal arch; ventrally it les on the abdominal wall 
about midway between the xiphoid cartilage and the pubis. 
32 
