THE BLOOD 115 



that a distinction should be made between the fluid in the 

 lymphatics and that which is not enclosed in vessels of any 

 sort. He would restrict the term lymph to the first appli- 

 cation, and would speak of the other as tissue-fluid. This 

 usage appears highly desirable, but is not as yet widely 

 current. 



Lymph, in the sense of tissue-fluid, cannot be collected 

 for analysis. Considering the delicacy of the capillary 

 wall and the probable freedom with which exchanges take 

 place through it, there is reason to believe that this fluid 

 must closely resemble the blood-plasma. When a tissue 

 is the seat of an active metabolism the income and outgo 

 of its cells must tend to alter the composition of the adja- 

 cent lymph and to make it less like the plasma. The 

 general effect will be to reduce the oxygen to a low level, to 

 raise the carbon dioxid content correspondingly, to con- 

 sume a fraction of the organic food, and to add miscella- 

 neous waste-products. The lymph which can be obtained 

 by cutting one of the larger lymphatics of the body has 

 these characters. This lymph may not be precisely like 

 the mixture which exists in close contact with the living 

 cells, but it is probable that the differences are not great. 

 According to a view formerly universal and still held by 

 many, lymph can work its way from any interstice of an 

 organ into the branches of the lymphatics, and so to larger 

 vessels of the same class. Many believe, however, that 

 there is a definite separation between the unwalled spaces 

 of the tissues and the interior of the true lymphatic system. 

 If this is the correct conception, we have good reason to 

 differentiate lymph from tissue-fluid. We may adopt 

 either view provisionally without being seriously misled. 

 Lymph contains white corpuscles and blood-plates. 

 Since it has in it some fibrinogen it may coagulate, but 

 owing to the absence of red corpuscles the clot is frail and 

 tremulous. 



