When nutrition is not at its best, the growth of muscle may be favoured by external pressure which squeezes lymph out of its tissue-spaces, and therefore leads to increased exudation from the blood. It is not improbable that in badly nourished tissues the circulation of blood is somewhat torpid and the lymph stagnant. A feeble circulation usually results in some œdema. The muscles, or rather the connective tissue which envelops and penetrates them, feels doughy, instead of being, as it should be, firm and elastic. Under these conditions massage is undoubtedly of service. Squeezing the muscles displaces lymph, and, if the pressure is properly directed, drives it along the lymphatic vessels. Fresh lymph exudes from the capillary bloodvessels, and the muscle-fibres, surrounded with a more abundant supply of nutriment, benefit, as, in a vigorous person, they benefit from use. Lymph is an exudate from blood. Its composition therefore depends upon that of blood-plasma, but it tends to differ from it owing to the influence of two causes. In the first place, the walls of the capillary bloodvessels restrict exudation. Red blood-corpuscles cannot pass through them. Proteins which are non-diffusible are, according to the circumstances of the tissues, held back to a greater or to a less extent. The pseudo-capillaries of the liver let them pass, as has already been said. The capillaries of the limbs restrict their passage to such proportions as, it may be supposed, are absolutely necessary for the nutrition of the tissues. In the second place, tissues remove food from lymph and add to it waste products. Hence the lymph issuing from a limb, after full contact with the tissues, contains less of the former and more of the latter—less sugar, for example, and rather more oxidized nitrogenous substances, lecithin and other things termed collectively “extractives,” because they can be extracted from dried blood or lymph by ether. The reaction of lymph is alkaline. After a time it coagulates, but coagulation is slower, and the clot less firm than in the case of blood.