THEOR Y OF HEIDENHAIN. 2 S 9 



Not so successful were Ludwig's attempts to demonstrate a direct 

 relationship between blood pressure and lymph formation. According 

 to Ludwig's hypothesis, the amount of lymph produced in any given 

 part must be proportionate to the difference between the pressure in 

 the capillaries and the pressure in the extra vascular spaces. In most of 

 Ludwig's earlier experiments on the subject this condition was found to 

 hold good. On leading defibrinated blood through a limb, the lymph 

 production in the limb was found proportional to the pressure at which 

 the blood was led through it. In the testis Tomsa 1 showed that ligature 

 of the pampiniforin plexus caused a large increase in the lymph from 

 this organ. Paschutin 2 and Emininghaus 3 found that, in the arm and 

 leg, extensive ligature of the veins led to an increased lymph production. 

 In all these cases, therefore, an augmented flow of lymph was obtained 

 by raising the capillary pressure of the part. On the other hand, the 

 two last-named observers were unable to prove any constant alteration 

 of lymph production incident on vasomotor changes. Thus, in one 

 experiment, Paschutin divided the brachial plexus of a dog and then 

 stimulated the cut spinal cord, so that there was constriction of all the 

 arteries of the body with the exception of those of the fore-limb under 

 observation. Even this rise of pressure had no effect on the lymph flow 

 from the fore-limb. A little later, Eogowicz, 4 working in Heidenhain's 

 laboratory, repeated Emininghaus' experiments on the hind-limb with 

 slight alterations, and found almost invariably a slight increase in the 

 lymph after section of the sciatic nerve or in consequence of active vaso- 

 dilatation. He proved, moreover, that the vaso-dilatation of the tongue 

 produced by excitation of the lingual nerve was followed by an increased 

 lymph production in the tongue, which might at times amount to an 

 actual unilateral oedema of this organ. 



Theory of Heidenhain. In dealing with the laws affecting 

 lymph production, we are hampered by the fact that, from the limbs 

 of an animal at rest, there is, under normal conditions, no lymph flow 

 at all, so that, when we wish to study the effects of our various 

 procedures on the lymph production in the limb, we have artificially 

 to bring about a lymph flow by kneading and massaging the limb. 

 This fact introduces at once an arbitrary element into the observa- 

 tion, and Heidenhain suggested, therefore, that the best mode of 

 investigating the truth of the filtration hypothesis would be to 

 experiment on the lymph flow from the thoracic duct. This physio- 

 logist carried out a long research on the various conditions under 

 which the lymph flow from the thoracic duct might be increased 

 or diminished, 5 and came to the conclusion that the results of his 

 experiments were irreconcilable with the filtration doctrine, and that we 

 must assume that the cells forming the walls of the capillaries take an 

 active part in lymph formation, i.e. that lymph must be looked upon as 

 a secretion rather than as a transudation. A very similar conclusion had 

 been previously arrived at by Tigerstedt, 6 mainly on theoretical grounds. 



Heidenhain's arguments may be shortly summarised as follows : 



1. Obstr action of the thoracic aorta causes a general fall of arterial 



!>. d. k. Akad. d. Wissensch., Wien, 1862, Bd. xlvi. S. 185. 

 2 Arb. a. d. physiol. Anst. zu Leipzig, 1873. 3 Ibid., 1873. 



4 Arch. f. d. ges. Physiol. , Bonn, 1885, Bd. xxxvi. S. 252. 



5 Ibid., 1891, Bd. xlix. S. 209. 



6 Mitth. a. d. physiol. Inst. zu Stockholm, 1886. 

 VOL. I. 19 



