206 PHYSIOLOGICAL PHYSICS. [Chap. xix. 



at once test to find whether this was the cause of the 

 variation. Again, albuminous urine is usually of ab- 

 normally low specific gravity, and in consequence a 

 urine of specific gravity of, e.g., 1*014, indicates the 

 necessity of testing for this abnormal constituent. 

 The variations, then, of the density of such a fluid 

 as the urine give important indications to the medical 

 practitioner. It may be noted that a solitary specimen 

 of urine ought not to be examined for its specific 

 gravity, as the density will vary according to the con- 

 ditions of the individual who passes it. The urine 

 passed during twenty-four hours ought to be collected, 

 mixed, and the specific gravity of this taken. 



The lactometer, or lactodensimeter, is gra- 

 duated for specific gravities varying from 1'04"2 to 

 1-014. 



Tho specific gravity of Imman milk is 1-0203 



cow's ,, 1-0324 

 ass's 1-0355 



cow's ,, 1-0324 



The subjoined tables afford a means of approxi- 

 mately estimating the quality of cow's milk. The 

 specimen of milk taken should be well shaken so as 

 mix the cream thoroughly, and air bubbles should be 

 removed. Then 



If the cream has been previously removed the specific 

 gravity of pure milk ought to be 1*037 to 1 - 033. 



A specific gravity of 1'033 to 1'029 indicates 10 

 per cent, added water, and every -003 below this an 

 additional 10 per cent, water. 



