XIV 



THE LYMPH 523 



induce a considerable increase in the formation of lymph, and 

 were therefore termed lymphagogues by Heidenhain. Such are 

 commercial peptone, extracts of crab's muscle, of the head or body 

 of leeches, the body of river mussels, the intestine or liver of dog, 

 egg albumin, curare, and (according to D' Errico) gelatin. All 

 these substances produce the same effect as regards flow of lymph 

 from the thoracic duct : immediately after the injection of the 

 lymphagogue into the vein, the lymph current increases as much 

 as four times, and the effect may last for over an hour. The 

 lymph becomes richer in proteins ; it subsequently becomes turbid, 

 then clears again : its coagulability diminishes or disappears. 

 This increase in the lymphatic current coincides with a slight fall 

 of arterial pressure, associated with acceleration of cardiac rhythm. 

 Starling holds that under these conditions also the lymph derives 

 principally from the liver, and is therefore more concentrated ; and 

 that if the portal lymphatics are ligatured there is no longer any 

 lymphagogic action after injection. Pugliese, however, has shown 

 that extract of crab's muscle and curare produce a marked increase 

 of lymph in the front limb of the dog as well, with a sensible 

 increase in its content of solids. Increased lymph formation 

 cannot therefore be considered as a phenomenon localised in 

 the hepatic capillaries. 



(&) As against these lymphagogues which increase the lymph 

 that is derived from the Uood Heidenhain ranges a second class of 

 substances, which are lymphagogues * because they increase the 

 lymph that comes from the tissues. Such are sugar, urea, sodium 

 chloride, and other crystalloid substances when injected in 

 sufficient quantities into the blood. They soon leave the blood, 

 abstracting large quantities of water from the tissues, which is 

 partly reabsorbed by the blood, partly goes to swell the lymphatic 

 current. The flow is accelerated ; the lymph becomes momentarily 

 turbid, and is reddish ; presently it coagulates slowly, although it 

 contains many crystalloids ; it is conspicuously poor in colloids. 

 The composition of the blood changes in consequence ; the water 

 increases, and the relative quantity of erythrocytes and haemo- 

 globin is lessened. The increase in the lymph stream is usually 

 associated with a slight rise of arterial pressure, proportionate in 

 each case to the quantity of lymph produced. 



The lymphagogues of the second series accordingly produce 

 changes in the blood and lymph of an opposite character to those 

 observed with lymphagogues of the first series. Their antagonistic 

 action is also shown by the fact that the latter do not excite 

 urinary secretion, while the former do,, so that the acceleration of 

 the lymph stream is parallel to the excretion of urine. 



V. These facts, as demonstrated by Heidenhain, were confirmed 

 by successive experimenters ; but they have given rise to various 

 interpretations. Heidenhain made them the basis of his secretory 



