MOVEMENT OF THE LYMPH. 



311 





muscle, carrying with it some of the waste products of muscular action, passes out of the 

 muscle into the fascia, between the now partially separated layers.] 



[Ludwig's Experiment. Tie a respiration cannula in the trachea of a dead rabbit ; cut 

 across the body of the animal immediately below the diaphragm ; remove the viscera, and 

 ligature the vessels passing between the thorax and abdomen ; tie the thorax to an iron ring, 

 and hang it up with the head downwards ; pour a solution of Berlin blue upon the peritoneal 

 surface of the diaphragm ; connect the respiration cannula either with a pair of bellows or an 

 apparatus for artificial respiration, and imitate the respiratory movements. After a few 

 minutes the lymphatics are filled with a blue injection showing a beautiful plexus.] 



(2) Within the lymph-trunks themselves, the independent contraction of their 

 muscular fibres partly aids the lymph-stream. Heller observed in the mesentery 

 of the guinea-pig that the peristaltic movement of the lymphatic wall passed in a 

 centripetal direction. The numerous valves prevent any reflux. The contraction 

 of the surrounding muscles, and pressure upon the vessels and the tissues, aid the 

 current. If the outflow of blood from the veins is interfered with, lymph flows 

 copiously from the corresponding tissues. [If a cannula be tied in a lymphatic of 

 a dog, a few drops of lymph flow out at long intervals. But if even 2^issive move- 

 ments 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 for by the non-striped muscle 

 which exists in the capsule and trabecular of the glands. AVhen 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) The lymph-vessels gradually join to form larger vessels, and finally end in 

 one trunk. Thus the 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 to 300 millimetres per minute in the large lymphatic in the neck 

 of a horse, a fact which enables us to conclude that the movement must be very 

 slow in small vessels. The lateral pressure at the same place was 10 to 20 mm., 

 and in the dog 5 to 10 mm. of a weak solution of soda, although it was = 12 mm. 

 Hg in the thoracic duct of a horse. 



(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 be- 

 come negative. [The diastolic suction of the 

 heart, by diminishing the pressure in the sub- 

 clavian vein, also favours the inflow of lymph 



'into the thorax.] 



(6) Lymph-hearts exist in certain cold-blooded 

 animals. 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 

 (fig. 225, L). They beat, but not synchronously, about 

 sixty times per minute, and contain 10 cubic centi- 

 metres of lymph. They have transversely-striped mus- 

 cular fibres in their walls, and are also provided with 

 nerve-ganglia. The posterior pair pump the lymph 

 into the branch of the vena iliaca communicans, and the anterior pair into the vena sub- 

 scapularis. Their pulsation depends partly, but not exclusively, upon the spinal cord, for if 

 the cord be rapidly destroyed, they may cease to pulsate, but not unfrequently they continue 

 to pulsate after removal of the cord. [And if the cord be destroyed gradually, they continue to 

 beat (Kabrhel).] A second source of their pulsatile movements is to be sought for in 



Fig. 225. 



Posterior pair of lymph-hearts (L) of 



the frog. 



