xiv THE LYMPH 513 



(direct method) may be replaced by an indirect method, i.e. the 

 fistula of the jugular or, as Jappelli advises, of the subclavian. 



The lymph which liows from the fistula of the thoracic duct is 

 a watery, slightly opalescent fluid, with a specific weight of 1012- 

 1022, less viscous than blood ; when left to itself it coagulates 

 slowly, forming a more tenuous and less copious fibrin reticulum 

 than that which forms in the blood. A small quantity of peptone 

 injected into the veins makes it incoagulable, although the blood 

 remains coagulable (Shore). 



When examined under the microscope it presents a certain 

 number of leucocytes precisely similar to those of the blood, 

 varying in size from 5 ^ to 10 //. The smaller and younger 

 leucocytes predominate in the lymph, the larger and adult 

 specimens in the blood ; but the total quantity contained in 

 1 c.mm. of lymph, though it varies considerably in different 

 animals and in the same animal under different circumstances, 

 seems not far removed from that of the leucocytes in the blood. 



A certain number of erythrocytes are also constantly present 

 in lymph, even when precautions are taken to avoid any admixture 

 with blood, or when the lymph which is moving through the 

 lymphatics of a living animal is examined. The lymph being 

 almost or wholly deprived of oxygen, the erythrocytes give a 

 brownish colour to the fluid ; but on contact with air, owing to 

 the transformation of the haemoglobin into oxyhaemoglobin, they 

 assume a clear red hue, which tinges the surface of the clot. It 

 is probable that some of these are not formed locally, but come 

 by diapedesis from the blood capillaries. So far as is known 

 at present there are no blood-platelets in lymph (Chap. IV. 9, 

 p. 118). 



The plasma ot lymph contains all the essential constituents of 

 blood plasma ; but the quantitative relations are a little different. 

 In particular it has been pointed out that lymph plasma, as 

 compared with that of blood, is poor in protein, which has been 

 partly absorbed by the tissues ; on the other hand, it is richer in 

 water and alkaline salts, so that its reaction is generally more 

 alkaline than that of blood plasma. For the rest, the chemical 

 composition of lymph varies considerably. According to the most 

 reliable of the existing analyses, the percentage quantity of water 

 varies from 93'5-95'8 ; the total solid residue is much less than 

 that of blood, varying from 4'2-6'5 ; the protein varies from 3 - 5- 

 4'3, fibrin from 0'04-0'06 : generally speaking, the protein content 

 diminishes owing to the muscular movements, and increases in 

 proportion with rest and sleep. The neutral fats, soaps, cholesterin 

 and lecithin are scanty in lymph (0'4-0'9 per cent) ; when it 

 sometimes looks turbid and highly opalescent this is due not to 

 fats but to protein compounds in a special state of aggregation. 

 It also contains a small quantity of sugar (dextrose). Some 



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