56 Veterinary Elements. 



widening out of the ureter. Blood is supplied the kid- 

 neys by the renal artery and removed by the renal veins. 

 If a section of a kidney is made, two portions together 

 with the cut ends, etc., of vessels and tubes, are seen; 

 the outer part being known as the cortex, the inner the 

 medulla. The kidneys afford the main road for the 

 throwing out (excretion) of broken down nitrogenous 

 material, the ammonia being evidence as to the charac- 

 ter of the waste material. The secretion of urine may be 

 considered as a filtering out of waste products from the 

 blood, water being its main constituent; in addition to 

 the filtration process, the kidneys cells have a selective 

 action, and take certain substances from the blood which 

 they change somewhat and later discharge into the urine. 

 The amount of the urine is inversely as the sweat; more 

 urine is passed in cold weather than in warm weather, 

 due to the greater blood pressure in the kidneys at that 

 time (e. g., winter). The urine of carnivora (dogs, etc. ) 

 is acid, clear, has more solids and is small in quantity, 

 whereas that of herbivora is turbid, poor in solids, alka- 

 line in reaction and great in quantity. When horses are 

 fed hay or straw only the urine is alkaline, when fed 

 oats principally, the urine is small in quantity, turbid, 

 acid and sticky. The urine of cattle and sheep is clear, 

 greenish yellow in color and poorer in solids than that of 

 the horse; that of the pig is clear, yellowish and alka- 

 line. Two tubes originate in the depressions of the kid- 

 neys and go to the bladder, one entering on either side; 

 they go through the coats of the bladder on the slant, 

 thus forming a valve which prevents the urine passing 

 back to the kidney; the tubes are known as the ure- 



