METABOLISM OF THE TISSUES. 491 



e.g., subcutaneously, when its presence may be detected in the urine 

 within 2 to 5 minutes. If the current from the tissues to the blood 

 is so active that the excretory organs cannot eliminate all the 

 effete products from the blood, then these products are found in 

 the tissues. This occurs when certain poisons are injected sub- 

 cutaneously, when they pass rapidly into the blood and are carried 

 in great quantity to other tissues, e.g., to the nervous system, on 

 which they act with fatal effect, before they are eliminated to any 

 great extent from the blood, by the action of the excretory organs. 



The effete materials are carried away from the tissues by two 

 channels, viz., by the veins and by the lymphatics, so that if these 

 be interfered with, the metabolism of the tissues must also suffer. 

 When a limb is ligatured so as to compress the veins and the 

 lymphatics, the efferent stream stagnates to such an extent that 

 considerable swelling of the tissues may occur (oedema, p. 419.) 



H. Nasse found, that the blood of the jugular vein is 0'225 per 1000 specifically 

 heavier than the blood of the carotid, and contains 0'9 parts per 1000 more solids; 

 1000 cubic centimetres of blood circulating through the head yield about 5 cubic 

 centimetres of transudation into the tissues. 



The extent and intensity of the metabolism of the tissues depend 

 upon a variety of factors. 



1. Upon their activity. The increased activity of an organ is 

 indicated by the increased amount of blood going to it, and by the 

 more active circulation through it (100). When an organ is 

 completely inactive, such as a paralysed muscle, or the peripheral end 

 of a divided nerve, the amount of blood and the nutritive exchange 

 of fluids diminish within these parts. The parts thus thrown out 

 of activity become pale, relaxed, and ultimately undergo fatty 

 degeneration. The increased metabolism of an organ during its 

 activity has been proved experimentally in the case of muscle, and 

 also in the brain (Speck). 



Langley and Sewell have recently observed directly the metabolic 

 changes within sufficiently thin lobules of glands during life. The 

 cells of serous glands (p. 283), and those of mucous and pepsin- 

 forming glands (p. 327), during quiescence, become filled with coarse 

 granules which are dark in transmitted light, and white in reflected 

 light, which granules are consumed or disappear during glandular 

 activity. During sleep, when most organs are at rest, the metabolism 

 is limited ; darkness also diminishes it, while light excites it, obviously 

 owing to nervous influence. The variations in the total metabolism 

 of the body are reflected in the excretion of C0 2 and urea, which 

 may be expressed graphically in the form of a curve corresponding 



