4 i2 SCIENCE PROGRESS. 



kidneys hyperasmic, and the lymph stream (in spite of the 

 fall of pressure in the aorta) began to flow more freely, and 

 its organic constituents became more abundant. 



Heidenhain considered that these experiments indicate 

 that filtration cannot be the main factor in the production of 

 lymph from the blood stream. 



In the latter part of his research, to which we now come, 

 an entirely different set of experiments supported this 

 conclusion. He follows up the suggestion originally made 

 by Rogowicz that substances exist which, like curare, have 

 a specific action in increasing the transudation from the 

 blood-vessels, just as diuretics increase the secretion of 

 urine from the kidney. To this class of substances he has 

 given the name of lymphagogues ; and these he further 

 divides into two classes. The first class cause an increased 

 flow of more concentrated lymph ; the plasma of the blood 

 is diminished in quantity and the amount of solids it con- 

 tains is also lessened. Long-continued obstruction of the 

 aorta annuls their action from injury to the secretory endo- 

 thelium of the abdominal vessels. The increased lymph 

 flow is derived from the blood. It may be called "blood 

 lymph ". In the greater number of cases the chemical 

 constitution of these substances is unknown, and the 

 materials are most diverse, consisting of extracts of muscles 

 of crabs and crayfish, heads and bodies of leeches, mussels, 

 dog's liver, peptone, and egg albumin. These substances 

 are supposed to stimulate the activity of the secreting endo- 

 thelium of the blood-vessels. 



The second class of lymphagogues contains, on the other 

 hand, such well-characterised chemical substances as grape 

 sugar, common salt, urea and other crystalloids. These in- 

 crease the lymph flow, but the lymph becomes more watery 

 than before. The blood at the same time becomes also more 

 watery, so that the excess of lymph cannot be derived from 

 the blood, but must come from the tissues. It may be 

 termed " tissue lymph ". Diuresis precedes and accompanies 

 the increased lymph flow. In the case of these lympha- 

 gogues a physical explanation will in part, but not wholly, 

 explain the phenomena ; the substances rapidly diffuse out 



