2 98 PROD UCTION AND ABSORPTION OF L YMPH. 
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 Colmheim, 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. Colmheim u. Lassar, Virchow's Archiv, 1878, Bd. lxxii. S. 132 ; and Jankow- 
ski, ibid., Bd. xciii. S. 259. 
