MOVEMENT OF THE LYMPH. 417 



the lymphatic wall passed in a centripetal direction. The numerous 

 valves prevent any reflux. The contraction of the surrounding muscles, 

 and every pressure upon the vessels and the tissues aid the current 

 (Ludwig, Noll). If the outflow of blood from the veins is interfered 

 with, lymph flows copiously from the corresponding tissues (Nasse, 

 Tomsa). [If a cannula be tied in a lymphatic of a dog, a few drops 

 of lymph flow out at long intervals. But if even passive movements 

 of the limb be made, e.g., simply flexing and extending the limb, the 

 outflow becomes very considerable and continuous.] 



(3.) The lymph-glands, which occur in the course of the lymphatics, 

 offer very considerable resistance to the lymph-stream, which must pass 

 through the lymph-paths, whose spaces are traversed by adenoid tissue, 

 and contain a few lymph-corpuscles. But this is, to a certain extent, 

 compensated by the non-striped muscle which exists in the capsule and 

 trabeculse of the glands. When they contract, they force on the 

 lymph, while the valves prevent its reflux. Enlarged lymphatic glands 

 have been seen to contract when stimulated electrically. [Botkin has 

 stimulated enlarged lymphatic glands with electricity in cases of 

 leukaemia.] 



(4.) As the lymph- vessels gradually join and form larger vessels, 

 and finally form one trunk, the transverse section, or sectional area, 

 diminishes, so that the velocity of the current and the pressure are 

 increased. Nevertheless, the velocity is always small ; it varied from 

 230-300 millimetres per minute in the large lymphatic in the neck of 

 a horse (Weiss), a fact which enables us to conclude that the move- 

 ment must be very slow in the small vessels. The lateral pressure at 

 the same place, was 10-20 mm., and in the dog 5-10 mm. of a weak 

 solution of soda (Weiss, Noll), although it was found to be 12 mm. 

 Hg. in the thoracic duct of a horse (Weiss). 



(5.) The respiratory movements exercise a considerable influence upon 

 the lymph-stream in the thoracic duct, and in the right lymphatic duct ; 

 every inspiration favours the passage of the venous blood, and also of 

 the lymph towards the heart, whereby the tension in the thoracic duct 

 may even become negative (Bidder). [The diastolic suction of the heart 

 by diminishing the pressure in the veins, also favours the inflow of 

 lymph into the thorax.] 



(6.) Lymph -hearts exist in certain cold-blooded animals (Panizza, Job. 

 Miiller). The frog has two axillary hearts (above the shoulder near the vertebral 

 column), and two sacral hearts, one on each side of the coccyx near the anus. 

 They beat, but not synchronously, about 60 times per minute, and contain 10 cubic 

 centimetres of lymph. They have transversely striped muscular fibres in their 

 walls, and are also provided with nerve ganglia (Waldeyer). The posterior pair 

 pump the lymph into the branch of the Vena iliaca communicans, and the anterior 

 pair into the Vena subscapularis. Their pulsation depends partly, but not 



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