128 
MAMMALIAN ANATOMY 
Examine longitudinal sections of the small intestine of the 
dog or cat. Note that the sections are so curved by the contrac¬ 
tion of the muscularis that the mucosa lies on the outer border of 
the section, the villi well separated. Under low power identify 
the layers, noting the occurrence of an additional thin muscle 
layer between the mucosa and the submucosa known as the 
muscularis mucosae; under high power study the details of villi and 
glands. Draw details showing (1) a longitudinal section through a 
villus , and (2) the form of a group of intestinal glands and their open¬ 
ings into the Imnen of the intestine. Occasionally compact masses of 
lymphoid tissue, known as solitary lymph nodules, will be seen in 
the submucosa. 
Study a preparation showing cross sections of individual 
villi. Draw one or two , as seen under high power. 
Study again cross sections of injected intestine to show the 
network of capillaries in the various layers, particularly in the 
villi. 
Study sections through various regions of the wall of the 
stomach. Note the same general arrangement of coats as in the 
intestine, with modifications in the form of oblique layers in the 
muscularis; the numerous deep folds of the mucosa, with tubular 
glands opening between them, peptic glands, of the simple or 
slightly branching tubular type in the region of the fundus, and 
pyloric glands, more branching and more convoluted, in form, in 
the pyloric region. Draw a view showing the general arrangement 
of layers as seen under low power; draw details of folds and glands 
of mucosa of the fundus and of the pyloric region under high power. 
Study sections of injected stomach to show capillary network, 
particularly of the mucosa. 
2. Special Digestive Glands. 
The primitive glandular structure, already studied in the case of 
the glands of the stomach and intestine, consists of an invagination 
of the epithelium, in the form either of a tube or of an alveolus, 
lined throughout with epithelial cells. When the invagination 
becomes so extensive and so complicated by branching that it 
forms a mass of tissue lying quite outside of the wall of the 
organ from which it arose, a distinct organ such as a salivary 
