136 DISEASES OF THE HOESE. 



ternal (medullary) part, made up in the main of blood vessels, 

 lymphatics, and nerves extending between the notch on the inner 

 border of the kidney to and from the outer vascular portion, in v\'hich 

 the secretion of urine is almost exclusively carried on; and (d) a 

 large, saccular reservoir in the center of the kidney, into which all 

 uriniferous tubes pour their secretions and from which the urine 

 is carried away through a tube g (ureter), which passes out of the 

 notch at the inner border of the kidney and which opens by a valve- 

 closed orifice into the roof of the bladder just in front of its neck. 

 The bladder is a dilatable reservoir for the retention of the urine 

 until the discomfort of its presence causes its voluntai-^^ discharge. 

 It is kept closed by circular, muscular fibers surrounding its neck 

 or orifice, and is emptied by looped, muscular fibers extending in 

 all directions forward from the neck around the blind anterior end 

 of the sac. From the bladder the urine escapes through a dilatable 

 tube (urethra) which extends from the neck of the bladder backward 

 on the floor of the pelvis, and in the male through the penis to its 

 free end, where it opens through a pink, conical papilla. In the mare 

 the uretha is not more than an inch in length, and is surrounded by 

 the circular, muscular fibers closing the neck of the bladder. Its 

 opening may be found directly in the median line of the floor of the 

 vulva, about 4^ inches from its external opening. 



GENERAL SYMPTOMS OF DISEASE. 



These appl}' especially to acute inflammations and the irritation 

 caused by stone. The animal moves stiffly on the hind limbs, strad- 

 dles, and makes frequent attempts to pass urine, which may be in 

 excess, deficient in amount, liable to sudden arrest in spite of the 

 straining, passed in driblets, or entirely suppressed. Again, it may 

 be modified in density or constituents. Difficulty in making a sharp 

 turn, or in lying down and rising with or without groaning, drop- 

 ping the back when mounted or when pinched on the loins is sugges- 

 tive of kidney disease, and so to a less extent are swelled legs, dropsy, 

 and diseases of the skin and nervous system. The oiled hand intro- 

 duced through the rectum may feel the bladder beneath and detect 

 any overdistention, swelling, tenderness, or stone. In ponies the kid- 

 neys even may be reached. 



EXAMINATION OF THE URINE. 



In some cases the changes in the urine are the sole sign of disease. 

 In health the horse's urine is of a deep amber color and has a strong 

 odor. On a feed of grain and hay it may show a uniform transpar- 

 ency, while on a green ration there in an abundant white deposit of 

 carbonate of lime. Of its morbid changes the following are to be 



