ITS SPECIFIC GRAVITY. 



21 



of solids is being excreted; for the total amount 

 of urine may be diminished owing to a defi- 

 ciency of water. 



By the density or specific gravity of a liquid, 

 we understand the expression of the weight of 

 a certain bulk of the liquid, compared with 

 the weight of an equal bulk of water. The 

 most accurate means of determining the speci- 

 fic gravity of a fluid, such as urine, is to have 

 a counterpoised bottle which is known to hold 

 a certain weight of distilled water at 60 Far., 

 say 1000 grs. It is exactly filled with the 

 urine of which we wish to know the density, 

 and then carefully weighed in a very delicate 

 balance. The weight of the liquid is of course 

 that of the bottle full of urine, minus the 

 counterpoise ; the weight indicates the specific 

 gravity or density. For example, if a counter- 

 poised bottle holds exactly 1000 grs. of distilled 

 water at 60, and when filled with a certain 

 sample of urine, it weighs 1025, we say that 

 the density of the urine is 1025 (compared 

 with an equal bulk of water which weighs 

 1000.) Although the most exact, the above 

 is for the practitioner by no means the most 

 useful method of determining the density of 

 the urine, for it necessitates the use of a deli- 

 cate balance, and the expenditure of consider- 

 able time. An instrument usually called the 

 urinometer, (Fig. 162), but to which the more 

 correct name of urogravimeter has been applied, 

 is the one best adapted for the ordinary observa- 

 tion of the medical or veterinary practitioner. 

 It is a small glass instrument with two bulbs, one 





