158 THE HORSE IN HEALTH AND DISEASE 



animals the color cannot be seen, as the skin is pigmented. The 

 "stocking" or filling of the legs is a form of passive congestion. It 

 may be prevented by hand-rubbing and applying bandages to the 

 legs as soon as the horse returns from work. A laxative diet 

 should be provided for such animals. The swelling which occurs 

 along the belly of a mare a few days or weeks before foahng is 

 another example. It is either due to a compression of the walls of 

 the veins, so that blood cannot circulate freely through them, or to 

 weakened heart action. In certain cases the watery constituents 

 of the blood may exude from the skin. The large milk veins of 

 some cows are often in a state of passive congestion due to a dam- 

 ming back of the blood into them. In such cases they are not an 

 index to the quantity of milk which the animal is capable of pro- 

 ducing. 



Anemia is the opposite of congestion. In this condition there 

 is either a diminution in the quantity or quality of the blood. It 

 may be either general or local. 



General anemia is due to a deficiency in the total quantity of 

 the blood. It is caused by excessive hemorrhage, poor nutrition, 

 or anything which destroys the red blood-corpuscles, particularly 

 parasites. Animals suffering from general anemia are said to have 

 "thin blood," their mucous membranes are palhd, and they are 

 listless. 



Local anemia is that condition in which there is less blood in the 

 part than normally, but the total amount of blood in the body 

 is not reduced. It is brought about by (1) pressure on the part; 

 (2) a thickening in the wall of a blood-vessel; (3) partial occlusion 

 of the artery to the part; (4) cold and chemical agents; (5) conges- 

 tion of - blood elsewhere in the body. The part affected feels 

 cooler and is paler than normal. If long continued, death of the 

 part takes place from lack of blood supply. 



Dropsy is a pathologic condition closely associated with altera- 

 tions in the blood. It may be defined as an abnormal collection 

 of a watery, straw-colored fluid in any body cavity or tissue. 

 The horse is less commonly afflicted than sheep and other ani- 

 mals. Two common forms of dropsy are ascites and hydrothorax. 



Ascites is an accumulation of dropsical fluid in the abdomi- 

 nal cavity. It is caused by anything that interferes with free 

 circulation of the blood, so that the blood is dammed back into 

 the veins. A poor diet and blood parasites, which alter the char- 



