392 



MANUAL OF PHYSIOLOGY. 



rough indication of the degree of concentration. On standing 

 and cooling a slight cloud of mucus often appears floating in the 

 fluid. This comes from the lining membrane of the bladder, and 

 it usually entangles a few flattened epithelial cells, which are the 

 only organized structural elements found in it in health. 



FIG. 175. 



Diagram showing the relation borne by the bloodvessels to the tubules of 

 the kidney. The upper half corresponds to the cortical, the lower to the 

 medullary part of the organ. The plain tubes are shown separately on the 

 right, and the vessels on the left. The darkly shaded arteries send <>fl 

 straight branches to the pyramid and larger interlobular branches to the 

 glomeruli, the efferent vessels of which form the plexus around the convo- 

 luted tubes. 



The fresh urine has a distinctly acid reaction. This does not 

 depend upon the presence of free acid, as is suggested by the fact 

 that no precipitate is formed on the addition of sodium hyposul- 

 phite, but upon the large amount of acid salts, particularly acid 

 sodium phosphate, which it invariably contains. A strictly veg- 



