520 PHYSIOLOGY CHAP. 



of lymph is essentially the effect of the activity of the living 

 cells which form the walls of the blood capillaries. For better 

 orientation in this difficult and complex subject we will tabulate 

 the different groups of facts brought forward and consider them 

 separately. 



A consensus of experimental results shows that increased 

 pressure in the blood capillaries is followed by increased formation 

 of lymph : 



(a) We know from the works of Emminghaus that the 

 occlusion of the veins in one limb not only increases the current 

 flowing through the cannula inserted into the lymphatic of that 

 limb, but considerably modifies the constitution of the lymph, so 

 that it becomes richer in erythrocytes and poorer in dissolved 

 solids. This fact is in agreement with clinical observation, which 

 shows that in cardiac failure, hepatic cirrhosis, thrombosis of the 

 veins, and in fact in every case in which there is obstruction or 

 local interruption to the venous circulation, with consequent 

 increase of pressure in the capillaries, the lymph transudes through 

 these so freely that oedema, i.e. stagnation or accumulation of 

 lymph in the tissue spaces, results. 



(b) Both Heidenhain and Starling obtained the same results 

 as Emminghaus after ligaturing the portal vein in the dog. The 

 marked rise of intra-capillary pressure in the intestine increased 

 the flow of lymph from the cannula in the thoracic duct four to 

 five times, with diminution of colloids and increase of red blood- 

 corpuscles. 



(c) On obstructing the vena cava inferior above the diaphragm 

 there is a marked fall of arterial pressure, in consequence of which 

 the viscera become anaemic, while there is still an acceleration of 

 lymph-flow greater than that which occurs after ligation of the 

 portal vein. The lymph does not contain more blood, but 

 becomes richer in solids, while at the same time clearer and 

 less coagulable. These results of Heidenhain were controlled by 

 Starling, who demonstrated that in the above experiments the 

 lymph was derived from the lymphatics of the liver and not of the 

 intestines, as Heidenhain believed. In fact, after the occlusion of 

 the vena cava, pressure increased below the point where the block 

 occurred, producing a corresponding rise of pressure in the hepatic 

 capillaries; on the other hand, the pressure in the portal vein 

 diminished (as shown by the blanching of the intestines) in conse- 

 quence of the marked fall of aortic pressure. 



(d) On occluding the thoracic aorta (by introducing from the 

 right carotid a catheter ending in a rubber balloon which could 

 be inflated by the injection of water), Heidenhain observed that 

 arterial pressure below the point obstructed could fall to zero, 

 while the lymph current might continue for 1 to 2 hours longer, 

 although with diminished velocity and progressive reduction. 



