nU VETERINAR^■ PATilOLOGV. 



Thus pneumonia is more prevalent during the seasons of sudden 

 change as early spring and late fall. 



Occupation. — The city express horse is particularly liable to 

 diseases of the feet, the thoroughbred to rupture of the heart 

 or blood-vessels, the dairy cow to udder diseases, the house 

 dog to indigestion, etc. 



Food and Water. — Excessive, insufficient or unwholesome food 

 and \vater, also irregularity of feeding or watering are fre- 

 quent causes of depressed condition of animals. In Holstein 

 an enzootic anemia destro\-s hundreds of suckling pigs annually. 

 The pigs are apparentiv normal until about twn weeks of age. 

 The cause is probably improper food and a predisposition result- 

 ing from excessive stimulation of the reproductive function of 

 the sow. Variegated color of parrots is produced by feeding 

 green parrots fat from siluroid fishes. Colic is essentially a 

 dietary disease. 



The effects of previous disease frequently leaves an animal 

 in a depleted condition, thus petechial fever is fretiuently a 

 sequel of pneumonia or "stable fever" (catarrhal fe\'er). 



Overz^'ork . lack of exercise, variable temperatures, and other 

 minor causes all have their influence in depressing the animal 

 body. 



Imitation. — Some animals, colts especially, have (a tandency 

 to imitate what other horses do, thus colts allowed to run with 

 cribbing horses occasionally become cribbers. 



E.xcI■i■I^'G cAi'SKS of disease are those acts or agencies which 

 directlv and specificallv produce disease as falling, stmlight, 

 chemic substances and infection. 



ileclianie. pliysie. eheniie and parasitic agencies are the principal 

 exciting causes of disease. 



Mechanic. — Diseases are produced mechanically by break- 

 ing the continuit^• of involved tissues, by compression, or by 

 changing the relations of anatomical elements. The condition 

 resulting from a break in the continuit}' of a surface soft tissue 

 is termed a wound, of sub-surface S(jft tissue, a rupture and of 

 osseous tissue, a fracture. Compression may cause bruisiu"- or 

 crushing depending upon the mechanical object inducino- the in- 

 jury, and the amount of pressure exerted. Luxations or dis- 

 locations are the result of changed relations of bones^ tendons 

 and ligaments. Volvuli and intussusceptions are the result of 

 changed relations of the intestine. Hernia is a condition in 

 which there is a changed relation, caused by a break in the 

 continuity of one tissue which permits an adjacent tissue or 

 structure to protrude or sacculate through it. 



