DISEASES OF THE LTKINARY ORGANS. 77 



of the sinuous secreting tubes leading from the sacs inward toward 

 the second, or medullary, part of the organ; (b) the internal (medul- 

 lary) part, made up in the main of blood vessels, lymphatics, and 

 nerves extending between the notch on the inner border of the kid- 

 ney to and from the outer vascular jjortion, in Avhich 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 gf (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 voluntary discharge. It is kept closed by circu- 

 lar muscular fibers surrounding its neck or orifice, and is emptied by 

 looj^jed 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 tlie 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 urethra 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 apply 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, j^assed in driblets, or entirely suppressed. Again, it may 

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

 (urn, 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- 



