The symptoms can be greatly relieved by careful attention to the diet. A limited quantity of roughage should be fed, and this should be good in quality and fed in the evening. During the warm weather, the animal should be watered frequently. After quitting work in the evening the animal may be allowed to drink as much water as it wants. Plenty of grain, soft feed and roots may be fed. A small handful of flaxseed meal given with the feed helps in keeping down constipation. Fowler's solution of arsenic may be given twice daily with the feed, in half-ounce doses for a period of ten days or two weeks. Chronic indigestion should be combated by digestive tonics. QUESTIONS 1. Name the organs that form the anterior and posterior air passages. 2. To what conditions are the injurious effects of keeping animals in a poorly ventilated stable due? 3. State the purpose of ventilation. How can the need of ventilation be determined in a stable? 4. State the causes of "cold" in the head; give the treatment. 5. State the cause of bronchitis; give the treatment. 6. What are the causes of pneumonia? Describe the symptoms and treatment. 7. What symptoms are characteristic of pleurisy? Give the treatment for pleurisy. 8. Give the causes and treatment of "heaves." CHAPTER IX DISEASES OF THE CIRCULATORY ORGANS GENERAL DISCUSSION.--The circulatory organs are the heart, arteries, veins and lymphatics. The _heart_ is the central organ of the circulatory system (Fig. 23). Its function is to force the blood through the blood-vessels. It is situated in the thoracic cavity between the lungs, and enclosed by a special fold of the pleura, the pericardial sack. There are two kinds of blood-vessels, arteries and veins. The _arteries_ leave the heart and carry the blood to the many different organs of the body. The _veins_ return to the heart and carry the blood from the body tissues. The _capillaries_ are small blood-vessels, microscopic in size, that connect the arteries with the veins. The arteries carry the pure blood. The opposite is true, however, of the lesser or pulmonary system. The pulmonary artery carries the impure blood to the lungs, and the pulmonary veins carry the pure blood back from the lungs. The _lymphatic vessels_ carry a transparent or slightly colored fluid and chyle from the tissues and alimentary canal. This system of vessels empties into the venous system. [Illustration: FIG. 23.--Photograph of model of horse's heart: auricle; ventricle; pulmonary artery; pulmonary veins; posterior aorta; and anterior aorta.]