LECTURE VIII 



CIRCULATORY AND LYMPHATIC SYSTEMS, AND 

 THEIR DISORDERS AND DISEASES 



PART I 



THE CIRCULATORY SYSTEM. 



401. The organs of circulation, in all animals, comprise — 



1. The Heart, which, so to speak, pumps blood through 



the body for purification and circulation. 



2. The Arteries, which carry blood to various portions 



of the body. 



3. The Capillaries, which form the connecting medium 



between arteries and veins. 



4. The Veins, which return the blood to the heart 



402. The Heart is a reddish -brown, hollow, cone-shaped 



muscular organ, situated between the right and left lungs, in the 



middle of the chest, or thorax (in other words, in the mediastinum), 



having a base which looks upwards, a body, and an apex pointing 



downwards in a slightly oblique manner towards the sternum, or 



breast-bone, inclining slightly to the left side. It is composed of 



involuntary muscular fibres, and is enclosed in a fine fibro-serous 



sac, or bag, called the pericardium, the surface of the heart being 



covered by a serous membrane — the epicavdium. In the horse and 



cow it is about 8 inches in length from the base to the apex, and 



weighs from 6 to 7 pounds. The walls on the right side of 



the heart are much finer and thinner than those on the left, whilst 



the walls of the left ventricle are about three times as thick 



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