340 A MANUAL OF VETERINARY PHYSIOLOGY 



nature of the diet ; the specific gravity is from 1016 to 1060, 

 depending on the diet ; the colour is pale yellow to straw-yellow ; 

 the urea varies from 4 per cent, to 6 or 10 per cent. On an 

 animal diet uric acid is excreted, but disappears on giving 

 vegetable food ; hippuric acid in small quantities appears with 

 fair regularity ; indican and phosphoric acid are well-marked 

 constituents, and a substance known as glycuronic acid may 

 be found, which exercises a reducing action on salts of copper. 

 The presence of bilirubin in the urine of the dog has been noted 

 by Salkowski. 



As an illustration of the variation of the dog's urine dependently 

 on the nature of the diet, we may take an example from a long 

 series of experiments by Bischoff and Voit. 



On a diet consisting of meat 0-57 pound, starch 071 pound, 

 salts 77-5 grains, a specimen of urine gave the following compo- 

 sition : 



Amount - 252 c.c. 044 pint. 



Specific gravity - - — 1049 



Urea - 2 ro grammes 326*6 grains 



Salts - - - - 5" 53 „ 85-6 „ 



On a diet consisting of meat 275 pounds and fat 0-55 pound, 

 the following was the composition : 



Amount - - - - 702 c.c. 1*23 pints 



Specific gravity - — io 54 



Urea - - - - 807 grammes 1,351 grains 



Salts - I2-2I „ 189 „ 



Glycuronic acid exists only in traces, but after the adminis- 

 tration of camphor or chloral it is obtained in well-marked 

 quantities. It is a point of practical importance to avoid 

 regarding urine which reduces salts of copper as necessarily 

 containing sugar, for glycuronic acid is itself reducing. 



The Discharge of Urine. — The urine is constantly being 

 secreted, and it either trickles down or is propelled down the 

 ureters to the bladder by rhythmic muscular contractions. It 

 is quite likely that both movements are employed, depending 

 upon the condition of bladder distension ; whereas ' trickling ' 

 is suitable for an empty bladder, some muscular effort on the 

 part of the ureters would be required when the bladder is full. 

 Either drop by drop or by ' spirts ' the urine enters the 

 bladder, which gradually advances in the pelvis, and rises up 

 in the direction of the sacrum. All reflux of urine into the 

 ureters is prevented by the oblique manner in which the coats 

 of the bladder are pierced, so that the greater the internal strain 

 the tighter are the ureters closed. If circumstances prevent the 



