being distributed to the mucosa, where it forms a subepithelial network and also surrounds the glands.

The nerves, which are both medullated and nonmedullated, pierce the serous coat and the outer muscular coat and form a complex network between the longitudinal and circular muscular coats, beset with micro

scopic ganglia. This network is called the plexus of Auerbach, and sends branches to the serous and outer muscular coats. Numerous branches are also given off to the submucosa, where they form another finer network (the plexus of Meissner), which in turn gives

off very fine branches to the epithelium, glands, and villi.

Lymphatics are very plentiful, beginning as blind canals situated between the glands, as lacteals within the villi, around the lymph-follicles, and in the muscular tissue. These canals communicate with a large plexus of moderate-sized lymph-vessels, which accompany the blood-vessels in the submucosa, and eventually pierce the muscular and serous coats to run within the peritoneal cavity

THE LIVER.

The liver is composed of five lobes, which are enveloped by a thin covering of fibrous tissue.

This fibrous tissue, which is very scanty and incomplete in man, but well marked in the hog, extends from the surface down through the substance of the organ (the capsule of Glisson), dividing it up into irregular lobules, which appear roughly hexagonal in sections.

The lobules are composed of tortuous rows of polyhedral, granular cells (hepatic cells), radiating from the center toward the periphery of the lobule.

The liver receives blood from two sources: viz., the portal vein and the hepatic artery. These vessels enter the organ at the transverse fissure and divide into small branches, which run between the lobules in the capsule of Glisson and are called the interlobular veins and arteries respectively.

The interlobular vein now sends a network of capillaries (the intralobular capillaries) between the rows of hepatic cells, to collect again in a small vein at the center of the lobule (the central or intralobular vein).

The interlobular branches of the hepatic artery divide up into capillaries, which are distributed to the fibrous

elastic tissue and, in the larger ducts, smooth musclefibers.

The acini vary in different glands from saccular to club-shaped or tubular. They are lined by a single layer of epithelial cells, broader and larger than those lining the ducts, which rest upon a membrana propria, or basement membrane.

According to the character of the secretion and the

general structure of the acini, the salivary glands are divided into the serous, mucous, and mixed glands.

The serous glands secrete a thin, watery, albuminous saliva. The alveoli are usually small and of the tubular variety.

The cells are opaque and markedly granular, and rest upon a relatively small basement membrane. The nuclei are usually round, and are placed about one-third

THE SALIVARY GLANDS.

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the width of the cell from the basement membrane. In the true serous glands the " demilunes” are absent.

The mucous glands secrete a thick, viseid fluid (mucus). The alveoli are usually larger than those in the serous glands, and are saccular or flask-shaped. The cells are larger, transparent, but slightly granular, have a well-developed basement membrane, and stain but slightly. The nuclei are usually flattened, and are placed close to the basement membrane.

In many alveoli we find, besides the large clear cells just described, thin, granular cells, or groups of cells, crescentic in form, and situated at the periphery of the acini, against the basement membrane. These usually have a spheric nucleus, and are known as the demilunes of Heidenhain, or the crescents of Gianuzzi.

The mixed glands, or seromucous glands, may have some acini of the serous type and some of the mucous, or some acini may contain cells of both kinds. It has been claimed that the demilunes could be considered as representing occasional serous cells situated peripherally in a mucous gland.

The blood supply of the glands is very abundant, the arteries accompanying the excretory ducts to a point near the acini, where they branch into a network of capillaries, which closely surround the basement membrane of the acini, and reunite to form the veins, which return parallel to the arteries.

The larger lymphatic vessels are found with the arteries in the interlobular connective tissue. These send along the course of the ducts branches which terminate in numerous irregular clefts or spaces around and between the acini.

Nerves are plentiful, and consist of medullated and nonmedullated fibers, with numerous small ganglia.

The ultimate distribution of the nerve filaments is

unknown, having been traced positively only as far as the basement membrane of the alveoli.

The Parotid Gland.

The parotid gland is a typical serous gland, and possesses the characteristics previously described under that head.

The excretory duct (Stenson's duct) is large, has thick walls of fibro-elastic tissue, and is lined by a double layer of epithelium. Its smaller branches are lined with a single layer of columnar cells, which present a distinctly striated appearance at their free edges, and are hence called rod epithelium.

Between the intralobular ducts and the acini intermediate or intercalated tubules occur. These are small tubules lined with flattened cells.

The Pancreas.

The pancreas is a gland of the serous type, and resembles the parotid gland so closely as to have been called "the abdominal salivary gland." It differs,

however, from the parotid in the following features :

The pancreatic duct (or main duct of the gland) branches directly to form the intermediate tubules without the intervention of the intralobular ducts, or salivary tubes of Pflüger, which in the parotid are lined with rod epithelium and are quite prominent.

The acini are longer and narrower, as a rule, than those of the parotid.

The secreting cells are more columnar, narrower, and their nuclei are usually slightly farther from the peripheral edges of the cells.

The cells also contain distinct, highly refracting granules (the zymogen granules), situated mostly at the margin of the cell-body next to the lumen. The