422 DIGESTIVE SYSTEM OF THE HORSE 
Lymphoid tissue occurs in the form of distinct nodules (Noduli lymphatici), 
which are either scattered or in groups. In the former case they are termed solitary 
nodules (Noduli lymphatici solitarii), in the latter aggregated nodules or Peyer’s 
patches (Noduli lymphatici aggregati). The solitary nodules are about the size of 
a millet-seed or a small sago grain. The patches are situated chiefly along the 
surface opposite to the mesenteric attachment and begin about three or four feet 
from the pylorus. They number one to two hundred, and are usually one to two 
inches (2 to 5 cm.) long and a quarter of an inch to one-half inch (ca. 2 to 14 mm.) 
wide. Larger ones occur in the terminal part, where one patch may have a length 
of seven to fifteen inches (ca. 17 to 38 em.) and a width of half an inch to one inch 
(ca. 5 to 25 mm.) in young horses (Ellenberger). They vary much in number, 
size, and distribution in different individuals, and undergo atrophy in old subjects. 
Vessels and Nerves.—The arteries of the small intestine come from the 
coeliac and anterior mesenteric arteries. The veins go to the portal vein. The 
lymph-vessels are numerous and go to the mesenteric lymph glands, thence to the 
Fic. 361.—LarGE AND SMALL AGGREGATED NODULES OR PreYER'S ParcHEeS OF SMALL INTESTINE OF HORSE. 
cisterna chyli. The nerves are derived from the vagus and sympathetic through 
the cceliac plexus. 
THE LARGE INTESTINE 
The large intestine (Intestinum crassum) extends from the termination of the 
ileum to the anus. It is about twenty-five feet (ca. 7.5 to 8 m.) in length. It 
differs from the small intestine in its greater size, in being sacculated for the most 
part, possessing longitudinal bands, and having a more fixed position. It is divided 
into cecum, great colon, small colon, and rectum. 
THE CCUM 
The caecum (Intestinum cecum) is a great cul-de-sac intercalated between the 
small intestine and the colon. It has a remarkable size, shape, and position in the 
horse. Its average length is about four feet (ca. 1.25 m.), and its capacity about 
seven to eight gallons (ca. 25 to 30 liters).!. It is conical in form, and is curved 
1 The length given here is measured from end to end along the side and midway between the 
curvatures. 
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