SEC. 10. THE NATURE AND MOVEMENTS OF LYMPH 

 (INCLUDING CHYLE). 



294. From what has been said in the preceding section 

 we are led to regard the multitudinous spaces, both small and 

 great, of connective tissue all over the body, including among these 

 the " serous cavities," as forming the beginning or roots of the 

 lymphatic system. Into these spaces certain parts of the plasma 

 of the blood transude and so become lymph ; (whether the epithe- 

 lioid lining of the large serous cavities plays any distinct part in 

 regulating the transudation of serous fluid, i.e. of lymph into those 

 cavities, we do not know ;) from these spaces the lymph is con- 

 tinually flowing through the lymph-capillaries into the lymphatic 

 vessels, and so by the thoracic duct and right lymphatic trunk back 

 into the blood system. 



The amount of lymph occupying the lymph-spaces, lymph- 

 capillaries, and minute lymphatic vessels of any region varies from 

 time to time according to circumstances. A hand, for instance 

 which has been kept hanging down for some time becomes swollen 

 and the skin tense ; if it be raised the swelling lessens and the 

 skin becomes loose ; and a similar temporary swelling of the skin 

 of the limbs, and of the skin generally, is frequently the result of 

 active exercise. Such a swelling is partly due to the blood vessels 

 being dilated, or to the return flow along the veins being retarded 

 so that the blood capillaries become distended with blood, but 

 is much more largely owing to the lymph-spaces and lymphatic 

 vessels of the skin and underlying structures being unusually filled 

 with lymph. On the other hand the skin may become shrivelled 

 and dry from a deficiency of lymph in the lymph-spaces and 

 vessels. Under even normal circumstances the quantity of lymph 

 in the tissues may vary considerably, and under abnormal circum- 

 stances a very large amount of lymph may greatly distend the 

 spaces of the connective tissue of the skin and other structures, 

 giving rise to oedema or dropsy. Obviously there are agencies at 

 work in the body by which the appearance of lymph in the spaces 

 or its removal thence along the lymph-channels, or both, may be 

 either increased or diminished. 



