292 PRODUCTION AND ABSORPTION OF L YMPH. 



source of the lymph, and secondly, the condition of the capillary 

 pressure in the organ or organs from which the lymph is derived. We 

 can determine the source of the lymph by a process of exclusion. 

 Tying the kidney vessels and lymphatics has no effect on the usual 

 consequences of obstructing the inferior vena cava. On the other 

 hand, if we ligature the lymphatics in the portal fissure which carry 

 off the liver lymph, we find that a subsequent obstruction has no effect 

 on the lymph flow, or indeed, may slightly diminish it. We must 

 conclude that the excess of lymph production consequent upon the 

 obstruction is entirely derived from the liver, and not, as Heidenhain 

 thought, from the intestines. The change in concentration is easily ex- 

 plained if we assume that, just as intestinal lymph is more concentrated 

 (i.e. richer in proteids) than the lyn^ph from the limbs, so the liver 

 lymph is more concentrated than intestinal lymph, or than the mixed 

 lymph obtained from the thoracic duct. 



In order to answer the question as to the cause of this increased 

 production of lymph in the liver, we must investigate the changes in 

 the circulation brought about by the obstruction. On obstructing the 

 inferior vena cava and recording the blood pressure in the chief vessels 

 of the abdomen, we notice that the pressure in the aorta drops almost 

 at once to a third of its previous height, whereas there is a very 

 considerable rise of pressure both in the portal vein and inferior cava. 

 It is probable that the effect of the rise of portal pressure on the 

 intestinal capillaries is more than counterbalanced by the severe drop 

 in arterial pressure, so that there is a fall of pressure in the intestinal 

 capillaries. This conclusion is borne out by the fact that, if the 

 abdomen be open, the obstruction of the inferior vena cava is seen to be 

 at once followed by blanching of the intestines, as Heidenhain pointed 

 out. On the other hand, the effect of the simultaneous rise of pressures 

 in the portal vein and vena cava must be to increase the pressure in 

 the capillaries of the liver to three or four times the normal amount. 

 We have then, as the results of this experiment, no rise of pressure in 

 the portal area and no increase of lymph flow from the portal area, a 

 large rise of pressure in the hepatic capillaries and a very large 

 increase of lymph flow from the liver. 



Influence of aortic obstruction. Another experiment, on which 

 much stress has been laid by Heidenhain, is the one in which 

 the descending aorta is obstructed in the thorax. The obstruction 

 of this vessel is easily effected by passing an indiarubber balloon, 

 tied on the end of a catheter, down the right carotid artery into 

 the aorta just beyond the arch. The results of this obstruction on 

 the lymph flow are somewhat variable. In most cases the lymph is 

 diminished to one-half or one-third its previous amount; in a few 

 cases the lymph is unaltered in quantity or even slightly increased. 

 In all experiments the amount of proteids in the lymph is increased. 

 Now, if we investigate the state of the circulation under these con- 

 ditions, we find that obstruction of the thoracic aorta causes a very 

 considerable fall of pressure in the aorta below the obstruction and 

 a corresponding fall in the portal vein, whereas the pressure in the 

 inferior vena cava is unaltered or in some cases even slightly increased. 

 We must conclude, therefore, that in the intestinal capillaries the 

 pressure has fallen considerably below its normal limits, while in the 

 hepatic capillaries the pressure is very little altered or may even be 



