Along the course of the lymphatic vessels numerous small bodies called lymphatic glands or follicles are found, which are composed of a delicate trelliswork of adenoid tissue, packed with nucleated protoplasmic cells, called lymph corpuscles, the combination making what is known as lymphoid tissue. (Fig. 83 (I h) and 85 (a),) These masses of cells and their delicate supporting reticulum are enclosed in a fibrous case or capsule from which branching trabecular pass into the gland and separate the portions of lymphoid tissue from one another. The lymph channels enter and pour their contents through the convex side of the capsule. The lymph then flows through irregular paths, which lie between the lymph follicles next to the capsule and trabecular, and lead to the concavity of the gland from which the efferent vessel escapes.

Lymphatic Network from between the Muscle Coats of the Intestinal Wall, with fine vessels and many valves, causing the walls to bulge.

Fig. 84. Lymphatic Network from between the Muscle Coats of the Intestinal Wall, with fine vessels and many valves, causing the walls to bulge. (Cadiat).

Section through the central or medullary part of a Lymphatic Gland, showing adenoid tissue.

Fig. 85. Section through the central or medullary part of a Lymphatic Gland, showing adenoid tissue (a) containing capillaries (b) and a fibrous trabecula (c) cut across showing a central artery. (Cadiat).

Clefts in the Corneal Tissue of a Frog treated with nitrate of silver, which leaves the spaces clear and stains the intermediate structure.

Fig. 86. Clefts in the Corneal Tissue of a Frog treated with nitrate of silver, which leaves the spaces clear and stains the intermediate structure. These clefts (a) and their processes (6) form the lymph canalicular system, and at the same time are the spaces in which the corneal corpuscles reside. {Klein).

These lymph glands occur in groups in the flexures of the limbs, the recesses of the neck, and the thoracic and abdominal cavities, a large number being placed in the mesentery, in the course of the intestinal lacteals.

In the submucous tissue of the intestine this lymphoid tissue is widely diffused, and here and there arranged in small follicles, which doubtless have a function similar to that of the lymph glands found elsewhere.