446 PRACTICAL PHYSIOLOGY 



the fluids thoroughly. Allow to stand in an upright position for twenty- 

 four hours, and then read off the graduation corresponding to the top 

 of the precipitate. This gives the number of grammes of dried albumin 

 per litre of urine used. If the urine has been diluted the necessary 

 calculation must be made in order to obtain the percentage in the 

 original urine. 



For more accurate estimation of albumin, Scherer's method is employed. 



ADVANCED EXPERIMENT. Place 50-100 c.c. urine (according to amount of 

 albumin in it) in a large-sized evaporating dish, and, while stirring, bring to the 

 boil. Carefully add a few drops of dilute acetic acid, and allow the coagulum to 

 settle down. If the supernatant fluid is opalescent, add a little more acetic acid, 

 and bring again to the boil. (It is very important to use as little acetic acid as 

 possible, so that acid albumin may not be formed.) The coagulum must then 

 be collected on a small ash-free filter paper which has been dried between 

 watch-glasses at 120 C. After being collected on the filter, wash the coagulum 

 with boiling water, followed by alcohol and ether, and dry it at 120 C. until the 

 weight is constant. Since the coagulum contains considerable ash, the filter and 

 coagulum must now be transferred to a weighed crucible, incinerated, and the 

 weight of ash deducted from the weight of dried coagulum. 



Mucus, Pus, and Casts in Urine. When the kidneys or urinary 

 passages are diseased, besides protein there may be a considerable 

 deposit of mucus in the urine. This body has the general properties 

 and solubilities of mucin (see p. 308), but may consist largely of nucleo- 

 protein. Casts also occur in the deposit from the urine. When these 

 come from the urinary passages, they consist of groups of flattened 

 epithelial cells. When they come from the kidney tubules, they are 

 tubular and consist of polyhedral cells, showing various stages of 

 degeneration. When the kidneys or urinary passages are infected by 

 micro-organisms, pus cells occur in the urine and form a deposit. 

 Strong potash dissolves the pus, forming a viscid solution. Pus also 

 gives a guiac test as for blood, but much more slowly and not after 

 boiling, which destroys the oxidases to which the test is due. The 

 only certain test for pus, however, is to examine the urine or deposit 

 with the microscope. The pus cells appear as colourless, spherical, 

 highly refractive granular bodies, about 9 /x in diameter, the nuclei of 

 which can be stained by adding dilute methylene blue. The urine is 

 usually acid when the pus comes from the kidney, and alkaline when 

 the pus comes from the bladder, due to the decomposition of urea and 

 ammonium carbonate. 



Haemoglobin in Urine. This may be due to bleeding from the 

 kidneys or urinary passages, when it is called haematuria, or to excre- 

 tion of haemoglobin or methaemoglobin from the blood plasma by the 

 kidneys, called respectively haemoglobinuria and methaemoglobinuria. 



