SEC. 8. THE NATURE AND MOVEMENTS OF LYMPH 



(INCLUDING CHYLE). 



§ 236. We are thus 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 ; (how far the epithelioid lining of the large serous 

 cavities plays a 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 continually 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 circumstances 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. 



399 



