492 METABOLISM OF THE TISSUES. 



with the activity of the organism ; this curve corresponds very closely 

 with the daily variations in the respirations, pulse, and temperature. 



2. The composition or quality of the "blood has a marked effect 

 upon the current on which the metabolism of the tissues depends. 

 Very concentrated blood, which contains a small amount of water, 

 as after profuse sweating, severe diarrhoea, e.g., in cholera, makes 

 the tissues dry, while if much water be absorbed into the blood, the 

 tissues become more succulent and even oedema may occur. When 

 much common salt is present in the blood and when the red blood- 

 corpuscles contain a diminished amount of 0, and especially if the 

 latter condition be accompanied by muscular exertion causing dyspnoea, 

 a large amount of albumin is decomposed, and there is a great 

 formation of urea. Hence, exposure to a rarified atmosphere is 

 accompanied by increased excretion of urea (Frankel, Penzoldt, and 

 E. Fleischer). Certain abnormal conditions of the blood produce 

 remarkable results; blood charged with carbonic oxide cannot absorb 

 from the air, and does not remove C0 2 from the tissues (compare 

 p. 31). The presence of hydrocyanic acid in the blood (p. 33), is said 

 to interrupt at once the chemical oxidation processes in the blood 

 (Mialhe), so that rapid asphyxia, owing to cessation of the internal 

 respiration, occurs (Ed. Wagner). Fermentation is interrupted by the 

 same substance in a similar way. A diminution of the total amount of 

 the blood causes more fluid to pass from the tissues into the blood 

 (p. 63), but the absorption of substances such as poisons or patho- 

 logical effusions (Kaup), from the tissues or intestines is delayed. 

 If the substances which pass from the tissues into the blood be 

 rapidly eliminated from it, absorption takes place more rapidly. 



3. The blood-pressure is of importance in so far that, when it is 

 greatly increased, the tissues contain more fluid, while the blood 

 itself becomes more concentrated, to the extent of 3-5 per 1000 

 (Nasse). We may convince ourselves that blood-plasma easily passes 

 through the capillary wall, by pressing upon the efferent vessel 

 coming from the chorium deprived of its epidermis, e.g., by a burn 

 or a blister, when the surface of the wound becomes rapidly suffused 

 with plasma. Diminution of the blood-pressure produces the opposite 

 result. 



4. Increased temperature of the tissues favours the metabolism, 

 so that the excretion of C0 2 and the production of urea are increased 

 ( 220, 221); while diminution of the temperature has the opposite 

 result ( 225). 



5. The influence of the Nervous system on the metabolism is 

 twofold. On the one hand, it acts indirectly through its effect upon 

 the blood-vessels, by causing them to contract or dilate through the 



