THE METABOLISM OF THE TISSUES. 449 



Atrophy resulting from reduction in the normal supply of blood gradually dis- 

 appears in the further course of time. 



In accordance with what has been stated a double current can be 

 recognized in the fluids of the tissues, the afferent current, which brings 

 the materials for the restoration of the tissues, and the efferent current, 

 which removes the effete products of metabolic activity. The former 

 will convey the albuminates, fats, carbohydrates, as well as the salts 

 in solution, as they are taken up by the organs of absorption, for the 

 formation of the tissues. It is clear that obstruction of any sort in the 

 arterial system of the tissue in question will diminish this supply. The 

 metabolism is as a result restricted, in consequence of deficient formative 

 activity. 



This current can be recognized from the circumstance that after injection of 

 a relatively indifferent, readily demonstrable substance, for instance potassium 

 ferrocyanid, into the blood, that substance will be found in the blood within the 

 tissues, whither it has been conveyed with the afferent current. 



The efferent current removes the products of metabolism, particu- 

 larly urea, carbon dioxid, water and salts, in order to convey these with 

 the utmost rapidity to the excretory organs. 



This current can be recognized from the circumstance that if a soluble sub- 

 stance be introduced into the tissues themselves, as with a syringe for subcutaneous 

 injection, for example potassium ferrocyanid, this will be found in the urine in 

 the course of a few (from two to five) minutes. 



If the efferent current from the tissues is so strong and so large that 

 the excretory organs are unable to eliminate the waste matters from it, 

 these may again wander through the tissues. Such a condition is ob- 

 served after subcutaneous injection of considerable doses of poisonous 

 substances, which often enter the blood in such large amount that, 

 before they can be eliminated, they are conveyed to other tissues, for 

 example the nervous system, upon which they exert their effects before 

 any considerable degree of elimination has taken place. If large amounts 

 of foreign substances are injected they may even be temporarily de- 

 posited partly in other tissues, particularly in the liver and the bone- 

 marrow. As the afferent current traverses two canal-systems, the veins 

 and the lymphatics, it is clear that obstruction of these paths will disturb 

 the metabolism as a result of interference with the normal removal of 

 effete matters. On tight constriction of a peripheral portion of the 

 body, in consequence of which veins and lymphatics are compressed, 

 stagnation of the current takes place to so marked a degree that even 

 swelling of the tissues may result. 



In the propagation of the currents in the tissues the activity of the 

 muscles is of great importance, inasmuch as not only do they favor the 

 movement of the fluid in the vessels by pressure within the yielding 

 tissues, but also where they are attached to the periosteum, the peri- 

 chondrium and the joints they cause changes in the form of the inter- 

 stices and thereby influence the movement of the fluid within the latter 

 by alternate contraction and relaxation. 



H. Nasse found the specific gravity of the blood in the jugular vein 0.225 

 in a thousand higher than that of the blood in the carotid artery, and contain- 

 ing 0.9 part more by weight in 1000 of solids. One thousand cu. cm. of blood 

 yield in circulating through the head more than 5 cu. cm. of transudate to the 



tissues. 



29 



