INFLUENCE OF PRESSURE FROM SURROUNDING PARTS. 543 



Influence of Pressure from Surrounding Parts. Con- 

 tractions of -the ordinary voluntary muscles, compression of 

 the abdominal organs by contraction of the abdominal mus- 

 cles, peristaltic movements of the intestines, and pulsations 

 of large arteries situated against the lymphatic trunks, par- 

 ticularly the thoracic aorta, are all capable of increasing the 

 rapidity of the circulation of the lymph and chyle. 



The contractions of voluntary muscles assist the lym- 

 phatic circulation in precisely the same way in which they 

 influence the flow of blood in the venous system ; and we 

 have nothing to add regarding this action to what has al- 

 ready been said on this subject in connection with the 

 venous circulation. 1 The fact that muscular movements 

 actually accelerate the flow of lymph has been conclusively 

 demonstrated by Colin, who found that when a tube was 

 introduced into any of the lymphatic vessels of the neck, in 

 the -horse or the large ruminants, the discharge of fluid in a 

 given time was increased one-quarter, one-third, and even 

 one-half, during movements of mastication. 2 



Increase in the flow of chyle in the thoracic duct, as the 

 result of compression of the abdominal organs, or by knead- 

 ing the abdomen with the hands, was observed by Magendie, 3 

 and the fact has been confirmed in all recent experiments 

 on this subject. The same effect, though probably less in 

 degree, is produced by the peristaltic contractions of the 

 intestines. 



When a tube is introduced into the upper part of the 

 thoracic duct, it is frequently the case that the fluid is dis- 

 charged more forcibly with each pulsation of the heart. 



Paris, 1851, tome i., p. 208 ; and POGGENDORFF'S Annalen der Physick und Che- 

 mie, Leipzig, 1832, Bd. xxv., S. 517.) 



1 See vol. i., p. 317 et seq., and page 325 cl seq., for the function of the 

 valves of the veins. 



2 COLIX, Traite de Physiologie Comparee des Animaux Domestiques, Paris, 

 1856, torne ii., p. 89. 



3 MAGENDIE, Precis tflementaire de Physiologie, Paris, 1836, tome ii., p. 

 183. 



