BLOOD. 225 



would be sufficiently proved by the structure of tlie organs 

 tlicmsclves, for they are permeated by such an extremely abun- 

 dant and dense capillary network, and such very delicate venous 

 twigs closely encircle their excretory ducts, that the tissue is 

 brought in contact with the blood at every point and in every 

 direction. 



The chemical constitution of these organs is likewise so pe- 

 culiar, that we might infer that the cells would exert a particu- 

 lar influence; for the muscular tissue, serous membrane, lung, &c. 

 when triturated with water, yield little else than some of the 

 constituents of the blood from the capillary vessels, while the 

 liver and kidneys by trituration yield a pappy mass, which is for 

 the most part soluble in water, contains much fat in a state of 

 suspension, and leaves only a small amount of solid residue 

 (18-9g in the liver, and, according to Berzelius, even less in the 

 kidneys), consisting of shreds of vessels and membranes. 



From the observations already made, we may infer that the 

 blood undergoes a much more rapid metamorphosis in the kid- 

 neys and liver than in the tissues of the muscles, bones, &c. If 

 it were possible to determine the time during which the same 

 blood remains in these organs, then we might decide with some 

 degree of certainty whether the blood which emerges from them 

 differs in its composition from that which enters them. We 

 have seen that there are reasons for assuming that the circula- 

 tion is delayed in these organs. If we suppose, with Haller,i 

 that the eleventh part of the whole blood passes through the 

 kidneys, and that, consequently, at each systole of the heart four 

 scruples are driven into them, then, assuming that the kidneys 

 contain from four to six ounces of blood, and that the rapidity 

 of the circulation in them is the same as in the aorta, the same 

 blood will remain in these organs for about one third or one 

 half of a minute. But taking into consideration the various 

 facts that we have adverted to regarding the impeded circulation 

 in these organs, we can scarcely doubt that the blood is detained 

 in them for a very considerable period. According to a calcu- 

 lation made by Keil, and quoted by Hales in his ' Medical 

 Statics,' the blood remains in the kidneys for several hours. 



R. Wagner 2 measured the rapidity with which a blood-cor- 



Elem. Phys., vol. 2, p. 167. - Lehrbuch der Physiologie, part 2, p. 193. 



15 



