146 THE URINE. 



centimeters measure the milk and pour it into the graduated flask, 

 adding as much as 90-per-cent. sulphuric acid (sp. gr., 1.82). Mix 

 by gently shaking until the curd has completely dissolved, then 

 revolve in the centrifuge at 600 to 800 revolutions per minute for 

 six or seven minutes. Always make duplicate tests, placing the 

 two bottles opposite each other in the machine. Now carefully 

 fill the bottles about to the highest graduation with hot water, 

 which should have been previously made ready, and whirl again 

 for one or two minutes. Holding the bottle in a perpendicular 

 position, read on the scale the differences between the upper and 

 lower margins of the fat which gives the percentage present in the 

 milk. If the test is successful the fat layer is clear or but 

 slightly cloudy. 



With breast-milk where the available amount is frequently 

 limited smaller flasks and less milk may be employed. Cream 

 must be diluted 5 to 10 times with water. 



THE UEINE. 



The urine is a solution which contains the final prod- 

 ucts from the chemical changes in progress in the animal 

 body. A part of these are excreted in the expired air and 

 from the skin, and a still smaller part through the mucous 

 membrane of the intestine, but, if we omit the carbon di- 

 oxid from the lungs, by far the greater proportion of these 

 final products is found in the urine. A study of its com- 

 position and variation, therefore, is often of great value 

 in judging of changes which are going on in the body. 



Among the most common inorganic constituents 

 normally found are the chlorids, sulphates, and phosphates 

 of sodium, potassium, calcium, and magnesium. Of the 

 normal organic compounds there are urea, uric acid and 

 its salts, creatinin, etc. The following, when found in 

 more than minute amounts, may be regarded as patho- 

 logical: Glucose, albuminous substances, blood, bile, pus, 

 fat, mucin, leucin, and tyrosin. Others which are more 



