240 THE LYMPH 



that the ligation of the hepatic vein is followed by an increased forma- 

 tion of lymph rich in proteins. This fact has been interpreted by this 

 author as showing that the lining cells of the hepatic capillaries possess 

 a true secretory power. Starling, on the other hand, came to the con- 

 clusion later on that it is due to the greater permeability of these 

 channels occasioned by a certain structural deficiency of their lining. 

 This diversity of opinion, however, does not lessen the weightiness 

 of the observations of Heidenhain, because while it is possible to in- 

 terpret this phenomenon in this way, a single exception of this kind 

 does not materially weaken the sum total of the evidence presented. 



Undoubtedly the most important facts brought forth by Heiden- 

 hain pertain to the augmentation of the lymph flow by means of sub- 

 stances which he has designated as lymphagogues. But, as these 

 agents not only accelerate the production of lymph, but also give rise 

 to lymph of a different concentration, they have been divided into 

 lymphagogues of the first and second class. To the former group 

 belong watery extracts of the dried muscles of crabs, crayfish and 

 leeches, the products of certain bacteria, extracts of liver and intestine, 

 peptone and egg albumin. In the second group must be placed all 

 crystaline substances, such as sugar, sodium chlorid and other neutral 

 salts. 



On injecting a lymphagogue of the first class into the venous 

 circulation, the flow of lymph is increased as much as six times the 

 normal. This quantitative change is associated with a greater concen- 

 tration and a lessened coagulability of the lymph, and may be obtained 

 with very small amounts of the excitatory substance. The blood 

 pressure, therefore, suffers no change whatever, and hence, this result 

 cannot justly be attributed to an enhancement of the conditions of 

 filtration. An even greater discharge of lymph may be obtained with 

 the help of the lymphagogues of the second class, but naturally, as the 

 introduction of these substances necessitates a solvent, it cannot be 

 avoided that the plasma of the blood and the body-fluid are thereby 

 rendered more watery. It is possible, however, to complete these 

 injections without markedly increasing the general blood pressure, 

 provided that the solution is permitted to enter slowly. It seems, 

 therefore, that the careful introduction of moderate amounts of water 

 as solvent cannot be seriously objected to, because it is not likely to 

 augment the capillary pressure in a measure sufficient to be able to 

 refer the increased flow of lymph to this cause. 



Great importance has been attached to the fact that the flow of 

 lymph continues for some time after death, and may even be height- 

 ened at this time by the injection of a lymphagogue. Strictly speaking, 

 however, this phenomenon does not actually prove that lymph is 

 formed after the blood has ceased to circulate, because it is quite pro- 

 bable that the tissue-fluid continues to seek the large lymphatics even 

 after the capillary pressure has been destroyed. Stress has also been 

 placed upon the fact that post-mortem lymph possesses a greater con- 



