The valiant leucocytes do their best to cope with all the rubbish, whether living or dead, that needs removal. They flock to any situation in which germs are numerous or tissue has been destroyed. If all goes well they take the foreign matter into their substance—dead tissue is matter foreign to the body—and either digest it in the course of their ordinary progress, or retreat with it, if they cannot digest it, to the nearest lymphatic gland. But in their efforts to reach objectionable matter they are apt to wander too far from the healthy lymph from which they obtain oxygen for their own respiration. Unable to breathe, they die. They lose the power of extruding pseudopodia. Their extensible, prehensile processes are drawn in. Assuming a globular form, they float helplessly in what once was lymph. Their body-proteins are largely changed to fat. As “pus cells,” they are thrown off in the discharge from an ulcer, or accumulate in the cavity of an abscess. A pus cell is a dead and fattily degenerated leucocyte. The third kind of breeding-place of leucocytes, a lymphatic gland, has a more elaborate structure than the tissues with which we have already dealt. Lymphatic glands are about the size of beans, and of the same shape. They are found in the course of lymphatic vessels in situations where they are not exposed to pressure, such as the back of the knee, the groin, the front of the elbow, the armpit, in the neck above the collar-bone, and on either side of the sterno-mastoid muscle, behind the angle of the jaw. There are a number in the abdomen and in the thorax. Each lymphatic gland is invested by a strong fibrous capsule. Its artery enters, and its vein and efferent lymphatics leave, the concave side (the hilus) of the gland. The lymphatic vessels which bring lymph to it pierce the capsule on its convex side. It is divisible into two parts: (1) The adenoid tissue which surrounds the artery and its branches; (2) the open network of “lymph-ways” which invest this adenoid tissue. Leucocytes divide in the adenoid tissue. The young lymphocytes drop out into the lymph-ways. As a stream of lymph, brought by the afferent vessels, is always flowing into the lymph-ways, and out by the efferent vessel or vessels, the lymphocytes are carried with it towards the thoracic duct. A lymphatic gland is therefore an organ for adding leucocytes to lymph in the course of the lymph-stream. It has, however, another and equally important function. Leucocytes which have picked up germs or other foreign matter pass on with the lymph to a lymphatic gland. After entering its lymph-ways they leave the lymph-stream, squeeze into the adenoid tissue of the gland, and there come to rest with their burden. They remain in the gland until the foreign matter is digested, or, if it be indigestible, until they undergo dissolution, when the particles of soot or pigment are deposited from their débris in a harmless state. When the skin is