348 THE LYMPH AND ITS MOVEMENTS 



chiefly in that the lymph is poorer in proteid. In comparison with the total 

 proteid of the plasma, the lymph is said to contain* less globulin. 



In the dog's lymph Hammersten found almost no oxygen, but found 

 thirty-seven to fifty-three vols. per cent of carbon dioxide. It is stated that 

 the carbon dioxide tension in the lymph is greater than in the arterial blood, 

 but less than in the venous blood. 



According to analyses at present available, the lymph of man contains: 

 93.5-95.9 per cent water, 4.2-6.4 per cent solids, 0.04-0.05 per cent fibrin, 

 3.5-4.3 per cent proteid, 0.7-0.8 per cent ash, 0.4-0.9 per cent fat, cholesterin 

 and lecithin. 



There are found in lymph also substances which have a marked influence 

 on certain parts of the central nervous system. If lymph from the cervical 

 lymph trunks of the dog be injected into the internal carotid of the same animal, 

 changes in the circulation are noted. Certain nervous mechanisms are stimu- 

 lated, others are paralyzed, and the form of the blood-pressure curve is altered. 

 Similar injections of blood have no such effect (Asher and Barbera). The 

 chemical nature of these substances is not yet perfectly known, but in all proba- 

 bility they are products of combustion in the organs. 



The quantity of lymph, inclusive of the chyle, which flows through the 

 thoracic duct into the blood stream in twenty-four hours may be estimated 

 for man at one to two liters. In view of the passage of certain constituents 

 into the blood by way of the capillaries, an exact determination of the quantity 

 of fluid flowing through the thoracic duct possesses no great interest. 



2. MOVEMENTS OF THE LYMPH 



To determine the flow of lymph quantitatively, a fistula is made in the 

 thoracic duct or in one of the larger lymphatics. The quantity which flows 

 from the thoracic duct immediately after the operation is fairly large owing 

 to the stoppage incident to tying-in the cannula, but it declines rapidly. In 

 the further course of an experiment of this kind the quantity may either 

 remain constant for a time, or may continue to fall; the latter appears to be 

 the rule. 



No lymph at all is to be obtained from the main lymph vessel of an 

 extremity, unless its flow is aided by active or passive movements of the part. 

 From this we may conclude that by far the greater part of the lymph flowing 

 from the thoracic duct, when the animal is perfectly quiet, comes from the 

 viscera. 



The lymph vessels are always full; the pressure of lymph in the cervical 

 trunk of the dog and horse is from 10 to 20 mm. soda solution. The velocity 

 of lymph flow is much less than the velocity of blood flow in vessels of 

 similar size. 



Among the forces which maintain the flow of lymph, the tension which 

 is exerted by the elasticity of the tissues should be ranked first; every increase 

 of tissue fluid must naturally heighten this tension and thus accelerate the 

 flow of lymph. The movements of the individual parts of the body whether 

 they be passive or active, occasion elevations of pressure on the lymph spaces 



