514 PHYSIOLOGY CHAP. 



observers have also found a considerable amount of urea. The 

 ash of lymph, like that of blood serum, oscillates from 0'7-0'S per 

 cent, and contains an excessive amount of sodium chloride, from 

 the lymph flowing from the thoracic duct in dog. Hammarsten 

 was unable to extract more than traces of oxygen and 37-53 per 

 cent of carbonic acid, i.e. a quantity greater than that contained 

 in arterial and less than that which can be extracted from venous 

 blood. 



This last fact shows that part of the carbonic acid developed 

 by the tissues is directly absorbed by the blood capillaries and 

 veins, both in the lymph spaces and in the lymph capillaries. So, 

 too, we must remember that many of the solid products of the 

 tissues are directly absorbed by the blood-vessels, and that the 

 lymph contains only such substances turned out by the blood as 

 are not taken up by the tissues (blood-lymph) and such products 

 of the tissues as are not directly absorbed by the blood-vessels 

 (tissue-lymph). The lymph spaces and capillaries thus represent 

 an internal medium in which the reciprocal exchange of materials 

 between blood and tissues takes place ; and the lymph vessels, 

 properly so-called, represent a drainage system which slowly, by 

 long and circuitous paths, reconducts all the residual matters, both 

 from blood- and tissue-lymph, left over from the direct exchanges 

 in the lymph spaces and capillaries, to the circulatory torrent. In 

 view of this it is evident that the quantity of lymph that flows 

 through the thoracic duct in the time-unit cannot be taken as a 

 measure of the total amount of lymph poured into the blood day 

 by day. According to Heidenhain, the average amount of lymph 

 flowing in 24 hours from the thoracic duct of a dog that weighs 

 10 kgrrns. is about 640 c.c. Noel Paton, from the thoracic duct of 

 a patient who weighed 60 kgrms., obtained about 1 c.c. of lymph 

 per minute, i.e. 1440 c.c. in 24 hours. From a woman, Munk and 

 Eosenstein obtained a quantity varying between 1200 and 2280 

 c.c. per diem. 



It is possible also to collect lymph from different parts of the 

 body by introducing a small cannula into the larger lymphatic 

 trunks of the upper and lower limbs, the liver, and the intestine. 

 The lymph from the limbs is similar to that flowing from the 

 thoracic duct of a fasting animal, but it contains a smaller amount 

 of solids (2-4 per cent). On the other hand, the lymph from the 

 liver contains more solids (6-7 per cent), even in the fasting 

 animal. That coming from the intestine during inanition exhibits 

 an amount of solids intermediate to the above. For the rest, both 

 the composition and the quantity of these various lymphs differ 

 considerably according to circumstances, especially in regard to 

 the degree of functional activity in the tissues and organs whence 

 they are taken. 



The large serous cavities of the peritoneum, pleura, peri- 



