298 PROD UCTION AND ABSORPTION OF LYMPH. 



laries of the liver. Their action, however, is not absolutely confined to 

 that organ. I have experimental evidence that there is a certain 

 degree of increased permeability of the intestinal capillaries after the 

 injection of these lymphagogues, an increased permeability which is 

 brought into evidence only after raising to a certain extent the pressure 

 in these capillaries. The first class of lymphagogues also affects the 

 capillaries of the skin. In a number of the experiments in which these 

 bodies have been injected, we may observe a rapid development of an 

 urticarial eruption on the skin, and it is a matter of common knowledge 

 that the ingestion of the animals from which these bodies are derived 

 (mussels, crayfish, lobster) is often followed in man by an eruption 

 of urticaria which may or may not be accompanied by other symptoms 

 of poisoning. 



Another substance which seems to act directly on the capillary wall 

 is curari. This body, however, differs from the class of lymphagogues 

 under discussion, in the fact that its chief action is on the vessels of the 

 limbs. The effect of curari in increasing the lymph production in the 

 limbs was noticed long ago by Paschutin working in Ludwig's labora- 

 tory. Its direct action on the endothelial wall of the capillaries can be 

 easily demonstrated in the living frog's web. It may be seen that, after 

 the injection of curari, the capillary walls become apparently more 

 sticky, so that the capillaries become filled with a number of leucocytes 

 adhering to their walls. 



Conclusions. Thus a renewed investigation of the facts discovered 

 by Heidenhain has shown that they are not irreconcilable with the 

 filtration hypothesis, but rather serve to support it. At the same 

 time they prove the extreme importance of the factor upon which 

 so much stress was laid by Cohnheim, namely, the nature of the 

 filtering membrane. In fact, we may say that the formation of lymph 

 and its composition apart from the changes brought about by diffusion 

 and osmosis between it and the tissues it bathes, depend entirely on 

 two factors 



1. The permeability of the vessel wall. 



2. The intracapillary blood pressure. 



So far as our experimental data go, we have no sufficient evi- 

 dence to conclude that the endothelial cells of the capillary walls 

 take any active part in the formation of lymph. It seems rather 

 that the vital activities of these cells are devoted entirely to maintain- 

 ing their integrity as a filtering membrane, differing in permeability 

 according to the region of the body in which they may be situated. 

 Any injury, whether from within or without, leads to a failure of 

 this their one function, and therefore to an increased permeability, 

 with the production of an increased flow of a more concentrated 

 lymph. 



We have no evidence that the nervous system has any influence on 

 the production of lymph in any part, except an indirect one by altering 

 the capillary pressures in the part through the intermediation of vaso- 

 constrictor or dilator fibres. This action is better marked in situations 

 where the capillaries are normally very permeable or where the per- 

 meability has been increased by local injury to the vessels, or by the 

 circulation of poisons in the blood stream. 1 



1 Cf. Cohnheim u. Lassar, Virchours Archiv, 1878, Bd. Ixxii. S. 132 ; and Jankow- 

 ski, ibid., Bd. xciii. S. 259. 



