LYMPH FORMATION 603 



is produced by an injection of bile or hsemoglobin. It seems 

 probable that Heidenhain's first class of lymphagogues are liver 

 poisons as opposed to cholagogues, and that they alter lymph pro- 

 duction in at least two ways ; by producing a pathological kata- 

 bolism of the cell protoplasm whereby the osmotic pressure of the 

 tissue fluids would be greatly increased ; and by altering the 

 capillary walls, and to a less extent the capillary blood pressure. 



(2) Asher suggests that obstructions of the inferior vena cava 

 increases lymph flow by increasing the activity of the liver, on the 

 grounds that it causes the same change in the blood and lymph 

 as does an injection of peptone. Since there is no reason for think- 

 ing that peptone acts in the way he suggests, there is equally no 

 reason for thinking that obstruction of the inferior vena cava 

 does. In fact, Asher on several occasions comes perilously near 

 to arguing in a circle. He observes an increased lymph flow, and 

 explains it by the very thing he has to show, namely, an increased 

 tissue activity. It seems probable that obstruction of the inferior 

 vena cava does alter the lymph flow by the same means as 

 Heidenhain's first class of lymphagogues, but there is no reason for 

 thinking that the means is increased physiological cell activity. 



(3) With regard to the action of Heidenhain's second class of 

 lymphagogues, Asher has tried to show two things firstly, that it 

 cannot be due to increased filtration, as Starling thought, and 

 secondly, that it is probably due to increased tissue activity, 

 aided perhaps by diffusion and osmosis. 



Asher found, like Heidenhain, that intravenous injection of a 

 concentrated sugar solution increased the flow along the thoracic 

 duct, and, like Starling, that if plethora was prevented by previ- 

 ous bleeding, no increased flow took place. But he has also shown 

 that if the injection is made a few minutes before the animal dies, 

 the increased flow still continues for several hours, and may reach 

 its maximum a quarter of an hour after death. It is clear that 

 Starling's explanation by increased filtration due to increased 

 capillary pressure does not suffice. Filtration may be a factor 

 in the living animal, but there must be another as well to explain 

 the post-mortem flow. Asher suggests that the older physical 

 explanation of Heidenhain, namely, that the crystalloid rapidly 

 diffuses out into the tissue space, and when there attracts water 

 from the tissues, meets the case. He has tried to confirm this 

 conclusion by the observation that when plethora is prevented by 



