54:2 ABSOEPTIOK. 



pable of producing a movement in the great trunk at the rate 

 of an inch per second. The great elasticity of the vessels 

 and the fact that they are never completely filled allow of 

 considerable distension of isolated portions of the lymphatic 

 system, when there is any obstruction to the current that is not 

 readily overcome. In this way we account for the variations 

 in the flow of the lymph and chyle which are of such con- 

 stant occurrence. 



Influence of the Contractile Walls of the Vessels. In. 

 treating of the anatomy of the lymphatic system, it has 

 already been observed that .the large vessels and those of 

 medium size are provided with unstriped muscular fibres, 

 and are endowed with contractility. 1 This fact has been 

 demonstrated by physiological as well as anatomical investi- 

 gations. Beclard states that he has often produced contrac- 

 tions of the thoracic duct by the application of the two poles 

 of an inductive apparatus. 2 It is not uncommon to see 

 the lacteals become reduced in size to a mere thread, even 

 while under observation. Although experiments have gen- 

 erally failed to demonstrate any regular rhythmical contrac- 

 tions in the lymphatic system, 3 it is probable that the vessels 

 contract upon their contents, when they are unusually dis- 

 tended, and thus assist the circulation, the action of the 

 valves opposing a regurgitating current. This action, how- 

 ever, cannot have any considerable and regular influence 

 upon, the general current. 4 



1 See page 43*7. 



2 BECLARD, Traite filementaire de Physiologie Humaine, Paris, 1859, p. 177. 



s COLIN is quoted as having observed rhythmical contractions in the mesen- 

 teric lymphatics in the ox ; but as far as we know, his experiments have not been 

 published. (LABEDA, Systime Lymphatique, Cours du Chyle et de la Lymphe, 

 Paris, 1866, p. 63.) 



4 In some of the lower vertebrate animals, in which the lymphatic vessels 

 have no valves, there exist several contractile dilatations, or hearts, which are 

 provided with valves, and which pulsate regularly. These were discovered by 

 Miiller, in 1832, in frogs, toads, and lizards. (MULLER, Manuel de Physiologie y 



