152 CIRCULATING FLUIDS : 



a partial change^ at least Wohler found that neutral potash, 

 or soda salts, formed by a vegetable acid, were decomposed in 

 the organism, and that the bases were removed by the urine 

 in the form of carbonates. "We thus see that the existence of 

 basic salts in the blood is indispensably necessary; and as neutral 

 or acid salts are usually contained in the food, it is clear that 

 they must undergo such a change in the body as to permit of 

 the removal of the acids by the urine while the bases are retained. 



There is every reason to suppose that the basic salts of pot- 

 ash and soda in the blood serve for the purpose of combining 

 with the lactic, fatty, lu-ic, and probably carbonic acids that 

 are continually secreted dimng metamorphosis. 



The salts of lactic and uric acid are in part excreted in that 

 form; and in part, as has been remarked, are decomposed, 

 so that the free acids are separated by the kidneys, while the 

 bases are retained. The salts of the fatty acids appear to be 

 secreted only in the liver. "Whether chloride of sodium, which 

 appears to be requisite for all the mammalia, serves merely for 

 the purpose of preventing the solution of the blood-corpuscles, 

 or whether it does not, like some other salts, act as a stimulant 

 on the nerves, and in that manner influence the composition of 

 the blood, is a question not easily answered. 



Active metamot'phosis of the blood. 



As the plasma is subjected to a continuous change in the 

 peripheral system during the nutrition of the tissues, it becomes 

 a matter of necessity that it should also receive a continuous 

 supply. This is afforded to it by the chyle, a fluid generally 

 only poorly supplied with blood-corpuscles, but abounding (at 

 least at certain times) in lymph- and chyle-corpuscles, and oil- 

 vesicles, and containing some fibriiv The chyle is therefore not 

 blood, although closely allied to it ; if, however, as is generally 

 believed, the chyle is the only nutriment of the blood, it must 

 ultimately be changed into blood, and this transformation is 

 eff'ected by an increase of the blood-corpuscles, and by a dimi- 

 nution of the lymph-, chyle-, and fat-corpuscles, while the fibrin 

 is not only increased, but becomes more plastic. A change must 

 therefore take place in the blood itself, and this must be not of 

 a passive nature, as during nutrition in the peripheral system, 

 but active; we must assume that there is a formation and de- 



