DISEASES OF HORSES 191 



secretion, are increased, and the surcharged urine proves irritant to 

 the urinary organs or the retained waste products poison the systems 

 at large. 



Diseases of the heart and lungs, by interfering with the free on- 

 ward flow of the blood from the right side of the heart, tend to throw 

 that liquid back on the veins, and this backward pressure of venous 

 blood strongly tends to disorders of the kidneys. Certain poisons 

 taken with the food and water, notably that found in magnesian. 

 limestone and those found in irritant plants, are especially injurious 

 to the kidneys. The kidneys may be irritated by feeding green vege- 

 tables covered with hoar frost or by furnishing an excess of food rich 

 in phosphates (wheat bran, beans, pease, vetches, lentils, rape cake, 

 cotton-seed cake) or by a privation of water, which entails a concen- 

 trated condition and high density of the urine. Exposure in cold 

 rain or snow storms, cold drafts of air, and damp beds are liable to 

 further disorder an already overworked or irritable kidney. Finally, 

 sprains of the back and loins may cause bleeding from the kidneys or 

 inflammation. 



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

 the discomfort of its presence causes its voluntary discharge. It is 

 kept closed by circular muscular fibers surrounding its neck or ori- 

 fice, and is emptied by looped muscular fibers extending in all direc- 

 tions forward from the neck around the blind anterior end of the 

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

 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. In 

 the mare the urethra is not more than an inch in length, and is sur- 

 rounded by the circular muscular fibers closing the neck of the blad- 

 der. 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, 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. 



Ip some cases the changes in the urine are the sole sign of dis- 

 ease. 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 

 transparency, while on a green ration there is an abundant white de- 

 posit of carbonate of lime. Of its morbid changes the following are 



