MOVEMENT OF CHYLE AND LYMPH. 415 



corpuscles, a considerable number seems to be dissolved; hence the 

 lymph, and also the blood, in this case contains more fibrin. 



Lymph-corpuscles are also dissolved within the blood-stream, and 

 help to form the fibrin-factors. 



201. Movement of Chyle and Lymph. 



The ultimate cause of the movement of the chyle and lymph 

 depends upon the difference of the pressure at the origin of the 

 lymphatics, and the pressure where the thoracic duct opens into the 

 venous system. 



(1.) The forces which are active at the origin of the lymphatics are 

 concerned in moving the lymph, but these must vary according to the 

 place of origin (a) The lacteals receive the first impulse towards the 

 movements of their contents the chyle from the contraction of the 

 muscular fibres of the villi (p. 390). When these contract and shorten, the 

 axial lacteal is compressed, and its contents forced in a centripetal direc- 

 tion towards the large lymphatic trunks. When the villi relax the 

 numerous valves prevent the return of the chyle into the villi. 

 (6) Within those lymphatics which take the form of peri-vascular 

 spaces, every time the contained blood-vessel is dilated the surrounding 

 lymph will be pressed onwards, (c) In the case of the pleural 

 lymphatics with open mouths, every inspiratory movement acts like a 

 suction-pump upon the lymph (Dybkowsky), and the same is the case 

 with the openings (stomata) of the lymphatics on the abdominal side 

 of the diaphragm (Ludwig, Schweigger-Seidel). (d) In the case of 

 those vessels which begin by means of fine juice-canals, the movement 

 of the lymph must largely depend upon the tension of the juices of the 

 parenchyma } and this again must depend upon the tension or pressure in 

 the blood-capillaries, so that the blood-pressure acts like a vis a tergo in 

 the rootlets of the lymphatics. 



[In some organs peculiar pumping arrangements are brought into 

 action. As already mentioned, the abdominal surface of the central 

 tendon of the diaphragm is provided with stomata, or open communi- 

 cations between the peritoneal cavity and the lymphatics in the sub- 

 stance of the tendon, v. Eecklinghausen found that milk put upon 

 the peritoneal surface of the central tendon showed little eddies caused 

 by the milk-globules passing through the stomata and entering the 

 lymphatics. The central tendon consists of two layers of fibrous tissue 

 arranged in different directions. When the diaphragm moves during 

 respiration, these layers are alternately pressed together and pulled 

 apart. Thus the spaces are alternately dilated and contracted, lymph 

 being drawn into the lymphatics (Fig. 164, h) through the stomata]. 



