164 THE HOHSE IN HEALTH AND DISEASE 



noticeable in the sexual glands of the aged and prematurely aged. 

 Brittleness of bones in the old is another example. Causes of 

 atrophy include all those factors which interfere with the nutri- 

 tion and activity of an organ. In starvation the fat of the body 

 disappears and the organs atrophy, so that the animal may lose 

 more than half in weight. Deficient nutrition, due to interference 

 with the normal blood supply, may occasion atrophy. This form 

 is seen when the chief artery to a part is Hgated. Constant pressure 

 inhibits growth and leads to a decrease in size, as may be seen in the 

 deep groove left across the nose of a horse tied for a long time by a 

 halter with a tight nose-band. In old horses the liver is smaller 

 than in young animals, due to long-continued pressure from other 

 abdominal organs. Continued lack of use causes an "atrophy of in- 

 activity." It is observed in the muscles after prolonged fixation 

 of a limb in splints. 



CALCULI AND CONCRETIONS 



Calculi are formed by the precipitation of salts which have 

 become insoluble. They may be found in the intestines, kidney, or 

 bladder. Intestinal calculi appear as rounded, stone-like bodies. 

 They usually weigh from 2 to 3 pounds, although one horse is 

 reported to have had a calculus weighing 16 pounds. Renal 

 calculi usually occur as soft, mortar-like masses in the pelvis of the 

 kidney, where they may be present for a long period without caus- 

 ing a visible disturbance. Cystic calculi form in the bladder from 

 nuclei the size of grains of sand. They may grow by accretion 

 until they are as large as a baseball. Some are quite smooth 

 externally, others are very rough and continually irritate the 

 bladder, causing the horse to urinate at frequent intervals. Sol- 

 vents for cystic calculi are not very successful. Operative treat- 

 ment by which they are completely removed is the only satisfactory 

 method to handle these cases. 



Concretions are formed of closely packed undigested vegetable 

 matter and are found only in the digestive canal. The hair-like 

 processes on the stems and heads of crimson clover which has been 

 allowed fully to mature before cutting may form "hair balls" when 

 eaten by horses and mules. To avoid this trouble such hay 

 should be fed in small quantities or mixed with other hay. If it is 

 sprinkled with water twelve hours before feeding the claim is made 

 that the danger of hair-ball formation is considerably reduced. 



