84 HORSE, SWINE AND POULTRY DISEASES 



ing on the part reflexly or as the result of some central nerve dis- 

 turbance affecting the branch which supplies a given organ. (4)' 

 Plethora and sanguinary temperament. Full-blooded animals are 

 much more predisposed to congestive diseases than those of a lym- 

 phatic character or those in an anemic condition. The circulation 

 in them is forced to all parts with much greater force and in larger 

 quantities. A well-bred full-blooded horse is much more subject to 

 congestive diseases than a common, coarse, or old worn-out animal. 

 (5) Fevers. In fever the heart works more actively and forces the 

 current of blood more rapidly ; the tissues are weakened, and it re- 

 quires but a slight local cause at any part to congest the structures 

 already overloaded with blood. Again, in certain fevers, we find al- 

 teration of the blood itself, rendering it less or more fluid, which in- 

 terferes with its free passage through the vessels and induces a local 

 predisposition to congestion. (6) Warm climate and summer heat. 

 Warmth of the atmosphere relaxes the tissues; it demands of the 

 animals less blood to keep up their own body temperature, and the 

 extra quantity accumulates in the blood-vessel system. It causes 

 sluggishness in the performance of the organic functions, and in 

 this way it induces congestion, especially of the internal organs. 

 So we find founders, congestive colics and staggers more frequent in 

 summer than in winter. (7) Previous congestion. Whether the 

 previous congestion of any organ has been a continuous normal one 

 that is, a repeated functional activity or has been a morbid tem- 

 porary overloading, it always leaves the walls of the vessels weak- 

 ened and more predisposed to recurrent attacks from accidental 

 causes than are perfectly healthy tissues. Thus a horse which has 

 had a congestion of the lungs from a severe drive is apt to have an- 

 other attack from even a lesser cause. 



The alterations of congestion are distention of the blood ves- 

 sels, accumulation of the cellular elements of the blood in them, and 

 effusion of a portion of the liquid of the blood into the fibrous tis- 

 sues which surround the vessels. Where the changes produced by 

 congestion are visible, as in the eye, the nostril, the mouth, the 

 genital organs, and on the surface of the body in white or unpig- 

 mented animals, the part appears red from the increase of blood; it 

 becomes swollen from the effusion of liquid into the spongelike 

 connective tissues ; it is at times more or less hot from the increased 

 combustion ; the part is frequently painful to the animal from pres- 

 sure of the effusion on the nerves, and the function of the tissue is 

 interfered with. The secretion or excretion of glands may be aug- 

 mented or diminished. Muscles may be affected with spasms or 

 may be unable to contract. The eyes and ears may be affected with 

 imaginary sights and sounds. 



Passive Congestion. This is caused by interference with the 

 return current of blood from a part. Old age and debility weaken 

 the tissues and the force of the circulation, especially in the veins, 

 and retard the movement of the blood. We then see horses of this 

 class with stocked legs, swelling of the sheath of the penis or of the 

 milk glands, and of the under surface of the belly. Tumors or 



