LYMPH FORMATION 599 



of plasma. In proof of the lymphagogue action of these substances 

 Heidenhain further pointed out that after prolonged obstruction 

 of the aorta they cease to act as lymphagogues, owing, he con- 

 sidered, to the death of the capillary endothelium. 



Starling showed by ligaturing the liver lymphatics that the 

 increased lymph flow comes chiefly from the liver, which accounts 

 for its higher concentration. He found the pressure in the 

 inferior vena cava unaltered, but that in the portal vein increased 

 owing to general vascular dilatation. He considered the rise 

 in portal pressure insufficient to account for the lymph flow for 

 two reasons : it would not very materially increase the pressure in 

 the liver capillaries, and it was found to last only about half 

 as long as the increased flow of lymph. He pointed out that 

 all these bodies are highly poisonous, and therefore unlikely to 

 stimulate a secretion, and explained their action by an alteration 

 in the other factor concerned in filtration, namely, the permeability 

 of the membrane. He considered that the power of these 

 substances to increase the permeability of the capillaries of the 

 liver, and to a less extent those of the intestines and skin as well, 

 is analogous to the action of curare and scalding on the limb 

 capillaries. He has explained that the reason why prolonged 

 obstruction of the aorta destroys the action of these lymphagogues, 

 is, not because a short obstruction does not lead to an increased 

 permeability of the hepatic capillaries, but is due to the fact that 

 prolonged obstruction so damages the liver endothelium that the 

 blood flow through the liver is seriously interfered with. 



Starling's interpretation of the action of these substances has 

 been criticised by Asher on the grounds that obstruction of the 

 aorta, while it prevents their action, can yet be shown to lead 

 to greatly increased capillary permeability. He showed that an 

 injection of normal salt solution, which alone produced no effect, 

 after occlusion of the aorta caused transudation into the serous- 

 cavities. Asher, however, admits that peptone alters lymph flow 

 by influencing the liver, and there is nothing in his observation 

 bearing upon either the blood flow through the liver or the per- 

 meability of its capillaries. 



A more serious criticism of Starling's explanation is that it is 

 no explanation but simply a restatement of the result. For, 

 except by the result, we have as yet no means of judging of the 

 permeability of diving membranes. And when, as here, more than 



